First off, decide how many tracks you want to record at on time. You will need enough mics (include cables and stands) to cover your needs. Your mixer will need seperate outs for each chanel or you will have to "pre mix" things down to the number of outputs on your mixer. A mono mixer- all chanels to 1 out, stereo mixer- all chanels to 2 outs, more outs on your mixer- more individual tracks to the recorder. To record multiple tracks you will need an interface which has as many inputs as the number of tracks you want to record at the same time. You will also need enough cables (and maybe adapters) to hook everything together. There are other things you might find usefull (converters, splitters, rack gear etc...) but these can be added as your budget allows. The gear list I described covers only the most basic needs for multitrack (simeltanious) recording. One more thing you will need (but you can't buy it) is patience, recording multiple tracks takes lots of patience, especialy when trying to record a whole band at once.
