Casting spells for dmg is pretty much pointless outside of ep4 with a few exceptions.
BattleFO is the way to go in most cases and very fun to play since there's a big range of weapons you can use.
Hundred souls, Lindcray, SoF, Bringers Rifle, UR, Rage de Glace and Rambling May are just a few examples I either already use or plan to get on my FOmarl. Glide divine and Tyrells Parasol are additional Weapons I run to do support stuff.
Playstyle is to s/d yourself and your group (obviously), use your glide to j/z all enemies, use rabarta to get control and beat them up with your weapons.
To compensate the low max ata on FOmarl , I use Agent K (+20 over cap), Kroe's Sweater (+10 over cap) and Smartlink (additional + 10 for ranged attacks)
Other units you want to look for are Adept, V502 and cent-battle (or v101 when you can't afford it yet)
You can still run your Nukebuild to hunt in ep4 but outside there, I woulnd't recommend it.
Fomar should play quite similiar, although there are some differences when it comes to gear choices.
I can't say much for Fonewearl since I have no experience with that class but I think her focus is a bit different and mostly on special attacks.
Anyways, hope that gives you some ideas on how to play a FO that's actually fun to play on this Server
If you still have questions or need input, feel free to message me. Just keep in mind that I'm still far away from perfect and there are plenty of better FOs than me on this Server so don't see this as a golen rulebook and more like a personal opinion from someone who likes to play FO.