bombs are worst in fsc, while guns are best, so its not really that great to go with bombs in fsc unless u want a challenge

Good advice: quit unbinding and selling your gear. Unless it has really good UVs, you won't be able to sell it at a profit compared to the CE cost of unbinding. Just sell your CE on the market if you're desperate for cash.

Your proposed bomber loadout is a good start. I'd add in an RSS, Nitro (for solo only, unless you really know how to use it), and keep the umbra driver around.

The RSS and Polaris both work splendidly on turrets, but having an umbra driver around can really take the frustration out of dealing with gremlin menders undoing all your hard work. You could also use a Callahan for covering both menders and silkwings.

Your loadout doesn't include any weapons that deal a decent amount of knockback at close range. If you're not very careful and/or have a good team, you might find yourself getting swarmed. Consider taking along a high-knockback sword like a Levi in cases where that could be a risk. The Levi's charge attack is also good against turrets.

Basically, you want to put together a list of wants, and then figure out how best to cover them. These should include: Bread and Butter DPS, dealing with turrets, dealing with menders, dealing with silkwings, dealing with getting swarmed, general crowd control and team support. Which of those are most important to cover depends on whether you're going solo, or with what the rest of your team is comfortable with covering.

A nice solo loadout could be: Nitro, RSS, Callahan, Levi. Or: DBB, VT, Polaris, Levi (great for fiend and undead levels). With a team to keep you out of trouble you might go: SB, EV, RSS, DBB. For RJ with a team a great combo could be: AoA, VT, GV and Umbra. For FSC with a team you might want: SB/VT, DBB, RSS, Polaris/BN.

@Glowing-Ember VV is a good option too, should have mentioned it.

And face it, the Levi is just a sword-shaped Nitronome. ;)

The electron/graviton bombs don't really come into their own until the 5* versions, at which point they start sucking up nearly every mob on the screen into a nice little easily-attacked wad in the middle. That said, they're also primarily combo weapons: you'll mostly be using them to hoover up enemies in order to unleash some other sort of attack on them (either yourself, or your teammates).

With your current loadout, though, you'll probably want to equip a DBB-line bomb first and leave the Electron Vortex for crafting later as you suggest.

Cooking up a spike shower first would probably get you a better payoff in the short term. After that I'd go for the Volcanic helm, then the Mad suit.

It's tempting to go for the Mad suit first, as you get both CTR and Damage bonuses, but if you go Volcanic Helm first you won't need to worry about the fire vulnerability at least on the Mad suit.

get a cata be both :D