There are several things you can do to.
- You can increase Dexterity to increase you overall chance to hit.
- You can increase Perception to decrease the range penalty. Perception also increases the number of action points you start with.
- You can increase Speed to increase the number of action points you start with and the number of action points gained each turn.
- You can increase Constitution to increase the maximum number of action points you can have. Constitution also increases Hit Points.
- You can get Expert Marksman up to 5 and then take the talent Quickdraw which allows you to fire an arrow for 3 action points instead of 4.
Notice that items that give bonuses to Primary Attributes may be better even if they are lower level and give less Armor Rating. As an example at the end of a game my ranger had Dex = 21 (12 Base +9 from items), Con = 13 (11 Base + 2 from items), Speed = 17 (14 Base + 3 from items), Per = 15 (Base 10 + 5 from items)