Does iMessage need wifi I'm concerned about it and I really want to use it. I haven't used it and I need some tips so someone please tell me if it needs wifi.
No - iMessage works over any viable network connection.

Assuming you are on an iPod touch, since WiFi is your only viable network, then it follows you need WiFi, but it's not a limitation of iMessage as much as it is of your hardware. iMessage works fine over ethernet, cellular data equally as well as WiFi.