Together, these factors make me think it could be taken down a notch, as I think spamming conditions like blinded generally doesn't lead to fun play patterns. Enemies may be greatly crippled or the DM will use entirely immune creatures as challenges. I like the idea of making this recover on a short rest, or upon taking one or more actions to restock with sand and dirt. This limits how often it can used in an encounter, and makes it more of a surprising trick and not a repeated fighting style based around flinging sand. Making the sand wear off at the start of the opponents next turn could also be used to weaken it slightly if needed - your whole team still gets a chance to counter-attack with advantage, but the enemy only needs to pass one saving throw to get their normal attacks against the rogue.
Together, these factors make me think it could be taken down a notch, as I think spamming conditions like blinded generally doesn't lead to fun play patterns. Enemies may be greatly crippled or the DM will use entirely immune creatures as challenges. I the idea of making this recover on a short rest, or upon taking one or more actions to restock with sand and dirt. This limits how often it can used in an encounter, and makes it more of a surprising trick and not a repeated fighting style based around flinging sand. Making the sand wear off at the start of the opponents next turn could also be used to weaken it slightly if needed - your whole team still gets a chance to counter-attack with advantage, but the enemy only needs to pass one saving throw to get their normal attacks against the rogue.
Together, these factors make me think it could be taken down a notch, as I think spamming conditions like blinded generally doesn't lead to fun play patterns. Enemies may be greatly crippled or the DM will use entirely immune creatures as challenges. I like the idea of making this recover on a short rest, or upon taking one or more actions to restock with sand and dirt. This limits how often it can used in an encounter, and makes it more of a surprising trick and not a repeated fighting style based around flinging sand. Making the sand wear off at the start of the opponents next turn could also be used to weaken it slightly if needed - your whole team still gets a chance to counter-attack with advantage, but the enemy only needs to pass one saving throw to get their normal attacks against the rogue.
TGETCE pg. 16
This is very interesting one. At first glance, this seems more powerful than many of the other 13th level abilities, being less situational and more combat focused, but it pays for that by forcing the player to choose between this or Uncanny Dodge. I think this is more of an offensive ability than Uncanny Dodge, as it allows a saving throw, and blinding a creature can give your entire party advantage against it, which also allows the rogue to trigger sneak attack without any assistance or special circumstances. Being able to blind a target on their turn, during an attack that is almost certainly their action for the turn, is also deceptively advantageous since every member of your party is guaranteed to take a turn before they have the chance to remove it, and it. This means that the duration is one of your turns, but two or one and a half of theirs, since this takes effect when you are targeted, before they roll the triggering attack. Since nothing stops you from blinding an already blinded opponent, this Page 290 of the PHB says about conditions
If multiple effects impose the same condition on a creature, each instance of the condition has its own duration, but the condition's effects don't get worse.
This means that once an enemy attacking the rogue repeatedly has been blinded, they would have to pass two saves in a row to get a sighted melee attack off.
TGE pg. 16
This is very interesting one. At first glance, this seems more powerful than many of the other 13th level abilities, being less situational and more combat focused, but it pays for that by forcing the player to choose between this or Uncanny Dodge. I think this is more of an offensive ability than Uncanny Dodge, as it allows a saving throw, and blinding a creature can give your entire party advantage against it, which also allows the rogue to trigger sneak attack without any assistance or special circumstances. Being able to blind a target on their turn, during an attack that is almost certainly their action for the turn, is also deceptively advantageous since every member of your party is guaranteed to take a turn before they have the chance to remove it, and it means that the duration is one of your turns, but two or one and a half of theirs, since this takes effect when you are targeted, before they roll the triggering attack. Since nothing stops you from blinding an already blinded opponent, this means an enemy attacking the rogue repeatedly would have to pass two saves in a row to get a sighted melee attack off.
TCE pg. 16
This is very interesting one. At first glance, this seems more powerful than many of the other 13th level abilities, being less situational and more combat focused, but it pays for that by forcing the player to choose between this or Uncanny Dodge. I think this is more of an offensive ability than Uncanny Dodge, as it allows a saving throw, and blinding a creature can give your entire party advantage against it, which also allows the rogue to trigger sneak attack without any assistance or special circumstances. Being able to blind a target on their turn, during an attack that is almost certainly their action for the turn, is also deceptively advantageous since every member of your party is guaranteed to take a turn before they have the chance to remove it. This means that the duration is one of your turns, but two or one and a half of theirs, since this takes effect when you are targeted, before they roll the triggering attack. Page 290 of the PHB says about conditions
If multiple effects impose the same condition on a creature, each instance of the condition has its own duration, but the condition's effects don't get worse.
This means that once an enemy attacking the rogue repeatedly has been blinded, they would have to pass two saves in a row to get a sighted melee attack off.
This looks like a very fun subclass - I don't even think it treads too close to anything that already exists, maintaining the Rogue's focus on useful bonus actions and reactions and making a rogue with a combat focus on par with the assassin subclass, but without the situational hyper-focus on the first strike damage. My initial impression is that a few class features are probably a little stronger than rogue subclasses, but not to a massive extent.
Bonus Proficiencies
Fun, flavorful, and unlikely to increase overall power outside highly unusual situations where players are deprived of normal weaponry or you want to attack with something really weird. This is practically a freebie that shouldn't unbalance anything.
Instigator
A strong ability when it's working, with an interesting set of restrictions that allow it to be worked around. This is more combat-focused than most other rogue subclasses 3rd level abilities, with the Assassin standing out as the only other purely fighting focused move. Let's compare it to the Armorer Artificer subclasses' Thunder Gauntlets, another third level ability with similar features.
TGE pg. 16
Thunder Gauntlets Each of the armor's gauntlets counts as a simple melee weapon while you aren't holding anything in it, and it deals 1d8 thunder damage on a hit. A creature hit by the gauntlet has disadvantage on attack rolls against targets other than you until the start of your next turn, as the armor magically emits a distracting pulse when the creature attacks someone else.
Comparatively, Instigator is more versatile and has a slightly longer range, but also requires a bonus action instead of being a rider on an attack and requires the target to understand you, making it ineffective against unintelligent enemies. As a minor side note, for flavor reasons you might consider making this ability ineffective against creatures immune to the frightened condition.
One strength of this ability to keep an eye on is the contested roll. Most conditions are applied via attack rolls or saving throws, and many powerful monsters are designed with features like Legendary Resistance to account for this, and tend to be more proficient in saving throws than Insight. Charisma isn't the most useful score for a rogue otherwise, but with a modest CHA bonus and Expertise this is still likely easier to land than an ability using a conventional delivery method. Additionally, since this is a bonus action it's adding a lot of dice rolls. I would consider RevenantBacon's suggestion of either rolling against a passive score, or if this is too consistent considering a CHA or WIS saving throw.
Shakedown
Situationally granting advantage on a specific skill check is consistent with the Thief and Inquisitor rogue abilities at 9th level, and this nicely fits that roll. The only thing I would be careful of with this ability is that it specifically improves bargaining on the price of goods and services. DMs have a wide range of stances on haggling. It's very a minor point, but I would list the advantage on information gathering first in the ability, since it's likely the more universally applicable one. Overall, unlikely to cause issues.
Pocket Sand
This is very interesting one. At first glance, this seems more powerful than many of the other 13th level abilities, being less situational and more combat focused, but it pays for that by forcing the player to choose between this or Uncanny Dodge. I think this is more of an offensive ability than Uncanny Dodge, as it allows a saving throw, and blinding a creature can give your entire party advantage against it, which also allows the rogue to trigger sneak attack without any assistance or special circumstances. Being able to blind a target on their turn, during an attack that is almost certainly their action for the turn, is also deceptively advantageous since every member of your party is guaranteed to take a turn before they have the chance to remove it, and it means that the duration is one of your turns, but two or one and a half of theirs, since this takes effect when you are targeted, before they roll the triggering attack. Since nothing stops you from blinding an already blinded opponent, this means an enemy attacking the rogue repeatedly would have to pass two saves in a row to get a sighted melee attack off.
Together, these factors make me think it could be taken down a notch, as I think spamming conditions like blinded generally doesn't lead to fun play patterns. Enemies may be greatly crippled or the DM will use entirely immune creatures as challenges. I the idea of making this recover on a short rest, or upon taking one or more actions to restock with sand and dirt. This limits how often it can used in an encounter, and makes it more of a surprising trick and not a repeated fighting style based around flinging sand. Making the sand wear off at the start of the opponents next turn could also be used to weaken it slightly if needed - your whole team still gets a chance to counter-attack with advantage, but the enemy only needs to pass one saving throw to get their normal attacks against the rogue.
I don't think this ability is game-breaking, but my experience with playing Monks and Stunning Strike has pushed me away from powerful and highly repeatable status conditions as generally not being terribly fun.
Comfortably Numb
This feels like one of the weaker abilities of the class. Resistance to all the physical damage types as a bonus action is very solid, but at 17th level big swathes of magical damage types are common. Evasion already helps rogues deal with many of those effects however, and on the whole it's still a good utility that's applicable in most fights, less situational than the Inquisitor or Assassin's 17th level abilities. I think immunity to charm is interesting, and that it would even be fun and flavorful to stick immunity to frightened on top of that, and that a short rest recharge feels fair.
Conclusions
All in all, I think this is a strong subclass, but not a broken one. There are a few things about Instigator and Pocket sand that might benefit from some streamlining, especially after some playtesting, but none of them feel like critical issues. This does a good job of being a more combat-focused rogue archetype without being as narrowly focused as the assassin, and I'd be happy to play with someone using this.