Should I buy Plasma Caster from Minerva? | Best uses of Gold Bullion?

Hey, y'all!

I'm coming back to the game but never really used Gold Bullion. I actually don't even know how I got 1350 of it.

Anyway: should I get the Plasma Caster plan from Minerva? Or should I use Gold Bullion with other stuff? I really don't know what can I get with it. Are there better things to get with this currency?

I'm starting to make a heavy build.

Thanks!