It really does depends on you. Why do you need more credit for? Are you eyeing a specific card for its cashback? Some people prefer to garden if they have enough limits and just ask for SP CLI rather than app then hurt their AAoA. What's your priority? HP is not a guarantee for approval. I myself stopped apping once I have 4 networks (visa, mc, discover and amex) then only apped when necessary like home depot and lowe's for home necessities.
Let us know what you decide on to do! Good luck 
When I started rebuilding I did notice once I went up to 7 cards. Util changes/HP's/and other small alerts didnt hit my scores as much as when I had 3 cards. Might be a fluke but I guess I fell out of the so called thin file class. But everyones credit is like a fingerprint. No one matches exactly. In the begining little util changes would affect me by sometimes 10-15 points. Now maybe 2-6 points. Main reason was to get to anything I purchase I get something back. Name of the bank on the card I could care less about. And its worked out well. Make sure it will be a card that you will use and be rewarded for it. Not just another acount to reach a certain number of accounts.
Try to get your FICO scores too and not rely on CK scores. Try Discover Scorecard for your EX FICO for free. CCT is wonky right now. Good Luck!
Edit: spread your apps at least 4-6 months too. No sprees.
