Starters aren't worth much because like you said, with some luck, many players can get them pretty easily through wondertrade. Breeders often give them out for free as well. However, Tepig and Cyndaquil are rare so you could breed them and use the GTS to complete the Dex to get a Shiny Charm. This key item boosts your chances of finding alternate color Pokemon, which sell like hotcakes.
Or, you can start breeding for Pokemon with maximum stats if you have a sizable Friend Safari, Ditto, or other resources. There are guides in Trade
Corner. Hope this helps.