Audio mixers and mixing desks are a big subject to cover in a small summery such as this, but some basic rules apply when selecting the type you need. If you are on the road it may be worth considering a powered mixer. This is were the power amplifier is integrated with the mixing desk, so you have just one unit, all be it somewhat heavier than a line level desk.
Check how many channels you need and also consider the mixer specification carefully, since stereo line music channels can often be counted as two extra input channels on mixing desk. Inputs can also be confusing, since any one channel may accept several inputs, such as a line level input for a music source, microphone input and auxiliary input.
There are number of useful small mixers in this section and this can be handy if you need to brake out one channel so that it will accept multiple sources. With perhaps just a simple gain control on each of the extended inputs, these simple and cheap mixers can often allow you to avoid buying a bigger main desk.
Most of the mixing desks here will have sufficient facilities for bands and general sound reinforcement systems. If you need something like multiple effects send and return on each channel its is worth checking the full specification by downloading the individual manuals often attached to the product. Contact firstname.lastname@example.org for any detailed requirements.