Yeah, I used to be Triumph. Or still am. Or something.
Anyway, you're just about to the point where you can start using Beasts. Beating the level 5 boss lets you recruit them. (pro-tip: go back in 14 days or later and beat the 5th floor boss again, but make sure he's poisoned when he dies. You get his conditional item drop, which you can sell for lots of fuck monies) Actually, you have to go back to the spot where the wolf was afterwards. Hope that makes sense. You'll be disappointed, tho. They're not that great- their best skill requires a prerequisite that lets them take hits for other team members but a glitch(maybe, maybe it was intentional) uses the OTHER characters def instead of the Beast's for determining damage. They do have a pretty cool smorgasboard of skills to fuck around with, tho. I created 3 beasts to fuck around with- Mange the Wolf, Colbert the Bear, and Maurice the Stupid Panda. I leveled them to around lv 5 and forgot about them.
Gunner's binds aren't very good, hit at a lower percentage than DH. Really can't recommend DH enough, they fucking rock balls. Fire-based techs for Ronin are the best- Orochi, Kienzan and Midareba all rock balls. Pumping points into clarity is also a good idea. Sword Landsknechts are good for hitting multiple baddies with all-slash. Once you're comfortable with your War Magus as healer tho I'd definitely sub out your Medic as they just kind of sit there in the mid game I've found.
Basically, don't be afraid to experiment tho. You can always rest and reset skills, just grind to make up those 5 levels. Of the five characters in my party right now, I retired my Ronin at level 30 to get another Ronin with beefed up stats and more skill points. I rested my War Magus and Hexer because I didn't like the builds I had going, and my Gunner and Dark Hunter I decided were fine. The important thing to remember is that when deciding to rest, figure out what you want the build at five levels less to look like. Remember you're going to be losing basically 5 points, so if you can't figure out how to reallocate in a way that benefits you don't bother to do it, just grind a bit.