Yep, knowing what you have in mind is essential to giving you a basic list.
I've kept eveything from a 4g pico up to my 125g reef so I've messed with every size. LOL It is immensely easier to work with a larger tank as a beginner setup. I started with a 29g which I found to be a perfect size.
I now have a total of 7 tanks up and running and one in the garage thats going up this week. You don't have to go bigger but it's an option.
What about looking on craigslist for a used biocube setup? If your total budget is $500 or so that will fit in nicely. If you wanted a new cube setup then you're looking at close to the budget max with the tank, heater and stand plus live rock and sand. Theres something to be said for an all in one tank, I have a 29g cube as well and the setup is simple to say the least. the lights are included and can keep a nice selection of coral and you can fit several fish including a clown fish pair.
Just some thoughts, let us know what you have in mind for the tank.