QQ is its own service, you can sign up for it independent of... well... whatever. So unless you want to tie the QQ to your account one way or another, it won't even matter.

Thou on that note, you can sign up for QQ using your email. Thou i'm not fully sure if you c*e a gmail based email. This is due to the fact that I'm fairly sure you have to click a confirmation link they will send you and... well... I'm not entirely sure if you QQ can send email to gmails because QQ is China based and gmail(and google in general) is blocked by the great firewall of China... so... Won't hurt to try thou.