Here are some known facts about Sayha Seer.
1. Seer is #1 PvP class. Not only in 1 on 1, but a geared & skilled lone Seer can wipe out the entire party of full Dark Gears. Believe me, I've seen it happen.
2. Seer is the least popular class for Party play...As you level, you will start finding that people don't want to party seer class. Seer is OK when geared enough but without proper gears, they get 1-2 shotted by the Raid Bosses, so naturally people don't want Seer in their party. Robe class + melee = weak, is what most people think.
3. Because of this, most seer players level by soloing...
How to Gear:
Basically, you gear your seer class just like feoh wizards. Gear-wise exactly the same, except you use 2H Retri as your weapon. If you read your passive skills you will understand. Also can't equip Sigil, so might as well use the Retri which has higher M.damage than caster or Buster.
How to Level:
If you want to level seriously, I recommend Choosing a Titan as your dual class and also level a Box iss at the same time.
It's a bit of investment to have the full gears for Both seer and Titan but it has a HUGH PAY OFF. You will be leveling so fast even after LvL 100.
I've found that geared titan can solo K85,k90,k95 easy but also...KAMA solo as well! All you gotta do is clear the trash and get the RB's HP down to 1%, use Scroll of escape, while Iss casts celestial(party invincibility skill), after Seer goes back to town to change to main class Seer, ISS can just kite the boss until Seer re-enters the instance, then ISS SOEs and re-enters!
Buff and Kill the RB! It's a lot of work and preparation but you will level so fast.