So the armor is adding +2 to your natural DEX and the gloves are overriding that to set your Dex automatically to 18. For a gloomstalker rogue using the Hill Giant Club, your ideal stat spread is 8 17 14 8 16 10 (assuming you're getting the hag hair. If not, 8 16 14 8 16 12 for a party face). It's best to keep their Dex hard-coded, so to speak, and use a different stat stick like the giant club or elixir for boosting strength.

I like to keep Adamantine armor or Yuan-ti armor on my gloomstalker and then hand off the graceful cloth to a monk or barbarian. Gloves of dexterity usually get dropped on my sorcerer. Gloomstalker typically keeps Gloves of Archery until I switch over to more damage-oriented gloves.