when starting out, all you really need is a 3 band eq (lo, mid, hi), and cue buttons (to headphone) for each channel. from there, just get what feels right, or what deal comes your way. vestax, numark, gemini, american dj, etc. all have entry level mixers so i suggest going to a place like steve's or long & mcquade and scoping them out...
..i don't know of any "mixer buyers guides" but i bet if you type that in to google, you'll get a pile of sites.
g'luck