(Note: I haven't been able to test anything in-game, so forgive me if I'm a bit behind on what things do. I'm working off of the Wiki and what's on the class page here, which seems to be behind for some other classes.)
Boomerang Dagger - So I decided to go with Boomerang Dagger for the no line of sight, and the fact it can cast itself again when it crits. The 4AP, 1MP cost isn't too high either so I can cast it a couple times and even more so if I manage to activate Rogue Master.
Longsword - The go to Air spell for most builds I see. Since I plan to keep range up on enemies and spam Boomerang while surrounding with a firewall, being able to push myself back plus for pretty great damage is a definite plus. Again, end-game I should have 10 AP so I can cast this multiple times as well if something's super close.
Flaming Claw - Now I'm not entirely sure on whether or not to use this or replace it, but for the time being I simply chose it as a low cost damage spell for Fire. Something else I can spam and also as another getaway so I can pull myself towards a party member.
Blinding Bomb - I went with this bomb over the others because of the lower cost, plus the -Range on distance monsters and PvP opponents.
(I messed around on Wakfu-Elements and figured I could get 4 spells at max 140 while I'll have the Earth tree in the 50's and the rest of the spells in Air/Fire at 47 or higher for resists and what not.)
Bomber Fan - Obviously this is for more damage on bombs, the +AP on explosions, and +Control.
Initiator - I decided to mainly level this up simply because I didn't like the idea of Runaway possibly screwing me over in a fight. Plus I assume I'll get Initiative from gear and the +Damage will be nice.
Rogue Master - The +Initiative goes well with Initiator, plus the chance to gain AP back from my Air spell usage allows me to spam more stuff.
Remote Control - Obviously to set my bombs off and add more damage to them.
Magnetic Claw - Like with other builds, it's mostly just for the push back. I also like the idea of running around holding a bomb like a crazy person until it's about to blow, then tossing it in someones face.
Boombot - I know most people don't run this for some reason, as to why I've no idea personally, but I'm gonna be having it spam Barbed Fire to reposition enemies back into my firewall and even set bombs off for me should I need it to.
As I said earlier, drop in a reply with your opinions and tips, I'd greatly appreciate it.