You don't have to keep it to the TCG if you're using stuff by Konami. You can use OCG and anime/manga-exclusives, too, if you want. Just keep them within reason. And you don't have to have a full Deck for your characters at the first Duel. When I said that, I meant that your list could literally have 10-15 cards total and I'd be fine just so long as it grew over time.