Every 10 dexterity grants an additional 20 accuracy rating. Every 10 dexterity grants 2% increased evasion rating.
Note that attributes include Strength, Dexterity, and Intelligence.
Both base Dexterity and attributes can stack dexterity. The following is an example: Astramentis Onyx Amulet. It adds 139 to all Attributes.
Stack dexterity by using crafting bench.
Passives can stack dexterity as well.