Ranger is one of my favorite classes to play in every mmorpg, so I have a ton of ideas on this class above all others
When I think of a ranger I think of a very fast and long range attacker with skills with generally no cast times who wears leather armor and a choice of:
Longbow with fast attack speed, longest range, and medium damage.
Shortbow with fastest attack speed, shortest range, medium damage.
Crossbow with Slowest attack speed, medium range, highest damage.
As for the 3 skill trees I would imagine
1. Nature based skills
Ranger is cousins with the druid class, so this tree would have synergy with the druid class. Focus in this tree would give you some HoT heals that allows you to be an off healer in a pinch or for solo playing, DoTs caused from poisons you can apply to your arrows, and rooting vine spells to immobilize foes.
2. Pure bow dps skills
Full of buffs that increase your bows speed/range/dps and bow skills that shoot your arrows in a outward cone aoe, hit all targets in a line, and fire multiple arrows quickly at a single target.
3. Stealthy ranger
This skill tree allows you to see hidden rogues within a certain distance and hide yourself with either no movement or very slow movement speed, skills could include a skill that teleports you away and stealths you while leaving a dummy behind, reduce the aggro you do, increase your dodge, and increase your general movement speed. Perhaps the typical snipe skill that has a LONG cast time and VERY high damage to a single target would be better in this tree instead of the pure bow dps tree?