Don't go with "not too pricey" ingredients. You'll end up with less than you expected.
"The pain of poor quality lasts longer than the satisfaction of a good deal"
I prefer St. Louis cut from central market. They are generally $4.99lb but I don't have to trim anything. Remove the membrane, season, cook. I can get whole uncut spares for $2.99 at sams but I'm not a fan of the flap. I figure that if I remove the flap then I'm back up to 4.99 anyway so what's the difference.
Baby backs are the most "forgiving" due to higher fat content, but hey have a higher fat content. Much more greasy end product.
Good luck. I'd recommend you ride the snake. Don't sauce till the very end. And use the 3-2-1 method.