Find a local reef forum. People get rid of stuff quite often. I got a 180G setup that just needed livestock rock and salt to get it running for 1000. You can probably find a Reef Ready tank for under 300 thats over 50 Gallons. Reef ready tanks have the overflow built in.
Buy base rock and skip the canister. For the 150-200 you spend on a canister, the 100 or so LBS of dry rock will do better in the long run.
What kind of corals will you want to keep? High light corals or a mix of high and low.Theres metal halide, T5HO, PC
and different variations of each to choose from.
If you go with a reef tank, I suggest having a sump/refugium to keep nitrate down. Also the sump can be used to hide a skimmer/ heater. A deep sand bed can also lower nitrate. All that you need to light it is a regular fluorescent.
Will you get an RODI
unit as well? Where are you located so i can find a local reef club for you.