Hmmm..
Ah, new member. Welcome to the forums.
If it's just Ballos you're having troubles with, there's some tricks to beating him.
During his first form, pull out your Nemesis and run up to him, close enough that you can point up and still hit him. He'll hit you once, maybe even twice, but if you're fast enough the combined firepower of the duel Nemesis' should finish him off quickly.
Form two will probably take the longest...
You can either waste HPs by getting onto his cheekbone and pointing up, spamming duel Nemesis' again, or use some of the Missiles you've got to hurt him when he lands and rests for a bit {Every third jump}. Make sure you save some missiles for form four, though.
For three, you'd probably be good just by spamming more Nemesis at all of the Eye rock things while dodging his attacks. Missiles if you're desperate.
For the last form, four, having a lot of Super Missiles comes in handy.
If you just spam them when he's done changing, you'll kill him literally in mere seconds.
So, to actually answer your question, for the Ballos fight I recommend sticking with the Nemesis and Missile Launcher V2. {Spur's also nice, but slow because of the charge}