Hey! I've got a budget of $150 and wanted to know what kind of used amp I could buy that would work as a gigging amp?
IDK? Where you from?   I got a Kustom Quad 100dfx I'd let go of for $150, but it would cost more than that to ship,  Sucker will blow the windows out of your house but its onboard effects suck,  Although on the clean channel it takes to peddles like a duck to water.  I just don't use it anymore and need the room for a new arrival,  
150 bucks is a really low budget for a gigging amp, any chance to increase that?

But I had a look on the Belgian ebay and i found this:

It's a Marshall 5212 fifty split channel reverb (basically they tried to make a transistor version of the JCM800) for 150€. It might not be the perfect amp for what you're playing, but I really doubt you could find something better within your budget.