I guess my thought here is, will you really benefit from each of those cards?
Looking at the limits, denials, and the specific cards themselves I can't see a particular strategy here. If I were in your position, I would probably just focus on continuing to rebuild with the cards you had (or I suppose have now), until whatever is causing the scores to be in the 600's is cleared up.
Once you are more in the 730+ range, applications for more rewarding cards will be approved but again you may want to sit down and figure out what exactly you're looking for, overall cash back or specific points that you will be using regularly enough.
I say this mostly because I know how exciting it is to click Submit and feel that anticipation while you wait for Approved to pop up. Eventually, you realize that you have useless cards and don't know what to do with them.
Figuring out what is most important to you will help you to plan out exactly which cards actually make sense in your wallet and give you the motivation to keep properly rebuilding so that you can eventually get them, with decent limits and APRs to boot.
