"planeswalker321"thanks for the advice.
I know some coin tricks that might work, but not linking rings or fire tricks,
Will sponge balls work? I am really good with them and I love to do it because it gets great reactions, and the I think crowd will be smaller when I start the show so everyone will be able to see them, so I think I should use sponge balls instead.
If you really love to do them, and are really good with them, then certainly you should use it. If you mean to use it while your crowd is small, make sure you're in an area with kids, because that's who it's going to attract. If you're busking, their parents will surely have money.
I also suggest, if you like working with sponge balls, looking into royal billiard balls, available on penguin for a buck fifty. It'll take a little more work to master, but it looks pretty neat when it's done.
If you have the standard set of four sponge balls, you could also try getting more sponge stuff to spice up the routine.
Did I suggest thumb tips yet? All sorts of stuff you can do with them. For the street, I suggest "burnt and restored bill," by Darwin.
Also, rope tricks. Professor's nightmare.