Welcome aboard
Good tank to start off with is either a 30 gallon or 55 gallon.
You will most likely spend as much on lighiting as you will on the tank+stand+canopy and then some. If you are going for an anemone then I suggest the 55 gallon tank, for lighting for say a BTA bubble tip anemone you will at least need 380 to 440 watts of VHO lighting, the lighting alone would cost near $300 dollars closer to $275. However when talking anemones Metal halide lights are the best, and you can double or triple the cost right there, just to give you and idea.
Spend a few days reading in this forum and in the Reef forum for some ideas, then decide on the size tank you want and we can help you set it up, then If you still want an anemone you should wait until the tank has matured a bit and stablized for about 6 months or a year.
Still want to do this?
Thomas