2 absolute requirements are it has to be a round wok
(means you have gas, just put a ring under it)
and carbon steel
if you have gas and are willing to put a ring on it when you cook (just put it on top when you want to whip out the wok, all asians just have it on the stove 24/7)
then we can talk shop
the cheapest thin carbon steel round wok in an asian grocer is great, but if would highly look out for a "hammered" wok, this means it's been hammered out (either by machine or crazy smith) and you can tell by the round hammer marks
i got mine from amazon (its an asian grocer in san fran that exports their retail store) if you have gas and want to go this route i can throw up links if you want.