definitely agree with Timbo...cutting corners is a recipe for disaster.
That being said, I wouldn't trade a single dollar I've spent (ok, maybe a few wasted ones) for the joy my family and I get from seeing our reef tank in every corner of our house. I just recently upgraded and can tell you...DO NOT SKIMP ON THE TANK. This is the most important part of reefing. you can't have an "aquarium" without the glass/acrylic to house them. I speak from experience in buying from a self-proclaimed "tank builder" who left me with a $1400 piece of junk I couldn't give away to even inexperienced aquarists. You do not need to spend lots of money here, but quality is so important. Look for sound seams and quality work. Last thing you need is a leak or failure. Buying used you are buying potential headaches. You have no idea the stresses their tank was put under, be it nicks and bangs, extreme heat or cold, etc. Go with new imo. Unless of course you go acrylic...that's a different animal and easier to find clean secondhand.
Things i was able to get second hand pretty easily were lighting fixtures (ATI Powermodules T5s, LEDS are everywhere) powerheads (mp40s, gyres) pumps, a sump, UVs, RODI filters, etc. Look here, but also Ebay, Craigslist, and other reefing communities. Even swaps. Local stores. Pennysaver even. Most equipment, I would trust buying used. Give it a good vinegar bath scrub and rinse and you're ususally good.
If you plan on using an auto top off for fresh water fill ups, buy new. In my opinion, these things crap out very easily. I keep one on hand in the box new bc I don't trust ANY of them.
Fyi as well, Do NOT skimp on live rock or sand either. Get nicely sourced, clean live rock, or go with "dead" rock and cycle the tank properly. Last thing you need is to introduce pests to a new tank immediately.
and then don't skimp on live stock. buy from a handful of reputable stores. you can find a good list from a search on here. last thing you need, again, is a case of velvet or ich devastating a new tank and all the money you've just spend.
all in all, accumulate slowly. look for deals and steals on second hand sights. bargain. this hobby is all about patience, so buy your equipment slowly just as you would cycle a tank slowly.
hope my 2cents helps. its a wild ride for sure and i learn new things everyday. follow my build thread for some ideas. I've gotten lazy as the tank prgresses but its certainly a joy. all "a couple thousand $$" i spent (according to what my wife knows) haha
