My .02...
Go with as large of a tank as you have room for. Despite what you might think, it's easier to be successful with a large system than to try and balance a small one. I, of course, did it the other way, and went from 5, to 10, to 29, to 75.
If at all possible, plan for a sump fuge. There are many advantages, but the most important for me, was the added water capacity / stability.
I'm sure other's will chime in here with lots of great info. Welcome to salt, and welcome to the board!