Well, for a gig, you will need (not you, the band)
A decent mixer, at least 8 tracks.
A decent PA system, you should count a watt for each people attending your shows, 2 if it's outdoors. That includes speakers, stands for the speakers etc...

As for your actual equipment, you can use a SM57 (shure microphone) to mike your amp, enter in the mixer, and go through the PA.

For the singer, something like a SM58 (shure)

The Bass player can go directly to the mixer (you'll need a direct box for that) or you can mike his amp like yours

The drums don't need to be amplified on a small gig. If you need to, you can use 2/3 mics at the very least, 8 being a reasonnable one (but now, if you play somewhere where you need to mike the drums, you won't have to worry about any kind of mixing problems anymore :) )

And also, it seems stupid, but Lights!!! I know that you can find real cheap halogen ones, that come with a stand and all.