Since I respect the purpose of this board, I'll keep my statements free of name brands, since I'm not sure what American DJ still sells (it's been a while since I've purchased new lighting).
I started my DJ'ing with some of the smaller lights and they actually produce a good amount of light. The only kind of light that didn't produce as much as I was hoping for was the kind that have the moonflower effect. Don't get me wrong, those are good for something "extra." There's NOTHING wrong with having some smaller lights, especially if you're just starting out.
I'd get at least two or three smaller lights, a couple of beacons, a strobe (or two), a rope light, and a medium to large mirror ball to get started with. Have enough lights that you can switch to and from throughout dances so you DON'T overheat them (I switch my lighting quite often during dances, so I don't burn-out the motors). Just my 2 cents
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Since I first started, I've purchased some more lighting along the way...there's always more lights that you can add to you lighting later.