If you want new...I'd say buy a 20g with Petco's dollar a gallon sale...maybe do the Tao LED
knockoffs in eBay for $80...$20 for sand...live rock depends on if you start live or buy dry and local prices, as some places charge outrageous prices. A hang-on-back skimmer would be good, but if you stay up on water changes, not absolutely necessary ($100ish?). Maybe $30ish for a heater if you need one where you are. Stands can vary depending on style and quality.
Look on places like Craigslist, as there are often great deals. I've got all four of my tanks there.
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