ross48:
I'm pretty sure extra GA time won't give you any advantage with RYR. I doubt it will hurt either. I would suggest you go ahead and do it if it is something you really want to, as you may not have that opportunity in the future (at least for a while), but don't do it as a stepping stone to RYR.
you do, however, need to be fully EASA before you apply to RYR.