For the first time grower, I would avoid the tuberous or tuberhybrida, as they are large growers and need a lot of strong light, and long days, they are not suited to house growing under most conditions. The species tuberous are small, but that is completely another story for a newcomer. If you want to grow from seed why not start with the wax (semperflorens), they germinate quickly and most can grow on windowsill although they can grow as tall as ten inches. I think a catalog for these seeds would be your best bet.

I started a couple of tuber begonias from seed in early Decmber '08 and they are just starting to bud. If you start from seed now, they'll want to flower in the fall, and I think the humidity levels and the light levels would be too low to sustain them. How about buying a potted one this year and overwinter inside?