Instant messaging help!

hi, I want to start sending instant messages to people but I don’t really know much about it. I was thinking about MSN as I think it is most popular among my friends but as I only have a gmail account and not a hotmail one, I don’t particularly want a new address, or is there a way to use MSN but keep my Gmail address? Someone suggested GoogleTalk to me which made sense seeing that I use gmail but I don’t know anyone else who has it, and you can’t IM people who have MSN from there right? So I was wondering if you could suggest an IM client that sounds right for me? Cheers