I did pretty well with a deck that had Amal'ja, Ixal, Moogle, Coeurl, and and Chocobo until I got better cards. Amal'ja, Moogle, and Chocobo all have 7s on at least one side and are easy to get.

Also the point of running primals or dungeons for cards is to get to 30 cards that you own. Even if you can't use them when you get them, that's still adding cards to your deck. And then when you hit 30 cards you can start using the rare cards you have.