Ive been wondering, If you want to get a multi engine rateing do you need to be instrument rated first?
No you don't.
Multi and IFR are unrelated.
The general idea is that a multi pilot should have a good pile of hours on his logbook cause twins have a tendency to be unforgiving of mistakes ... so generally pilots that go for multi already have the IFR ticket.
But that's not necessary nor a requirement that I know of ... if you are a good pilot you can just get a multi rating and fly VFR all the time. Nothing wrong with that ;D
Edit: I am talking about the USA here ... I don't know how it work in other countries. It might be different.