If I'm not mistaken co doms are base morphs, anything that isn't designer aka 2 base morphs together. So pastel and spider are base morphs but pastel is a co-dom and spider is a dominant. With ball pythons it isn't just basic dominant and recessive morphs, co-dom's, like mojaves and pastels, are also base morphs. Designer morphs would be like bumble bees or super pastels.

What I've seen recommended is to either buy a couple single gene or normal females and then after a year buy a couple two gene males. Thats my plan anyway. I got a mojave male earlier this year to make sure I was up to keeping ball pythons and so far I love him. I'm starting to save up now and hopefully next summer I'll have the money for a lesser female and a ghost female. After that i'll get one more male, I really like the axanthic morph and the bee's but everyone makes bee's.

http://www.worldofballpythons.com/morphs/ is a great resource for looking up morphs and if you plan on breeding to see what morphs you need to make the snakes you want.

Good Luck!