If by target competitions you mean the regular GNAS target (FITAs, Yorks/Herefords etc), then 60#.
If you are new to archery and/or compound bows beware of buying them second hand. I would seriously recommend getting lots of advice from someone with kowledge and that you trust. All sorts of pitfalls from dangerous bows to wrong draw length etc. If you are fully experienced, then ignore this.