Ring of Sharpshooting isn't required and doesn't actually synergize with the Shared Upgrades talent because it doesn't increase the level of the thrown weapon; it only increases the damage and durability.

To play sniper, all you need to do is dump upgrades into a single thrown weapon. Shuriken is ideal because it doesn't spend a turn to throw when you spot an enemy while moving.

Here's how it works:

1. You spot an enemy while on the move.
2. Throw +8 shuriken at them (instant)
3. Use Sniper ability with an unaugmented bow (instant)
4. Use normal bow attack if they are still alive.
5. Enemy now gets their first attack.

If they were a ranged enemy, now they get their first attack, but they're dead because they're squishy. Shuriken is the best because you can kill ranged enemies before they even know what's happening.

If you augment your bow for damage, it's unlikely they survive step 3, but now even your normal attacks are slow. You risk getting jumped on my rippers and such. With good enchantment, a speed augmented bow is amazing. With a high level thrown weapon, your 3 quick arrow hits will deal upwards of 30 damage each.

A +8 to +10 thrown weapon is usually sufficient, and you can use the rest for armor, wands, and rings. The Troll blacksmith helps a lot with reforging thrown weapons, so don't use the second or third shuriken or whatever.

Other choices for the thrown weapon:

1. Boomerang. It comes back! Fun with a damage augmented bow because during the two turns the sniper shot takes, the boomerang comes back.
2. Tomahawk. Massive bleed damage.
3. Force Cube is AOE, ~~but it still has to actually hit your primary target.~~
4. Literally any other. You just need it to be upgraded to trigger Shared Upgrades. It's fun to experiment with them.

Make liquid metal from other thrown weapons to then make Telekinesis to get your upgraded thrown weapon unstuck from bosses, or to pick it up in a pinch from across the room.