As far as I know (and I could be entirely wrong but I doubt it) this site does not sell cards. It's more of a gathering place to build and critique decks and get mtg news.
Feel free to use the deck builder and show us your deck. You might get some helpful tips, too.
As for MTGO cards, I usually use MTGOTraders or CardHoarder. Haven't had a problem yet and I always get the cards quickly.