In my experience, going from 0 to 2 revolving TLs caused an immediate score increase. Yes, new accounts will hurt a bit, but FICO loves it when you have at least one open revolving account. When you have 0 revolving accounts, the boost you get from adding a CC more than makes up for the slight damage caused by the new account.
I went from 590s to 630s just from opening two revolving TLs.
After the first or second CC though, then I have found what Sylvia said to be true. Once a couple of CCs are established, any further CCs will ding the score a bit until they age.
This was my experience. YMMV.