[quote name='Ryukahn']Also, I can trade for growlithe and ditto even though I don't have a national dex, right?[/QUOTE]
Yes, you can. I only had two badges, and I actually bought 6 Pokemon on eBay a while back. I'm sure they're hacks or something, but it doesn't bother me. I purchased a Mewtwo (I've ALWAYS wanted one), a Mew, Meowth, Igglybuff, Rayquaza, and a Ditto. The transaction maybe cost me $3. I've since breeded with my Pokemon Ranger Manaphy to get Phione, and of course, created Piplups, Chimchars, and Turtwigs after trading different level 1 newborns.
(My fiance and I couldn't stop laughing the other day during this breeding process. He was at my computer playing World of Goo, and I was nearby playing Platinum, saying, "C'mon breed! Gotta sell your babies!")