Welcome aboard! It hasn't been that long ago when I got started fly fishing, and I can tell you from experience, without this site, i'd never have made it. As to answer your questions, I think most everyone will say a 5wt is a good place to start, if you are only fishing streams, ponds and such. I don't know anything about fishing the saltwater, though I'd love to try sometime. Best advice though, is just get out on the water and go fishing. And practice casting alot. Although, I think you'll be better off if you practice about 20 to 30 minutes at a time. that way you don't get tired and start bad habits. Don't be bashful asking your questions, there is a ton of information available here on this site as well as the web, but sometimes that is overwhelming, so don't be bashful.

good luck and again, welcome aboard,
hNt