I think where your bodyfat is right now, a solid 4-5 month show prep would be absolutely sufficient for getting into contest shape without a struggle. You could potentially do it quicker if you put a ton of work in. So take that for what it's worth. Big picture, you obviously want to put on more muscle to be competitive at a high level. But if you're really just looking to get on stage now, you could start prepping whenever you see a show coming up that you want to do, and get that experience under your belt. But yea, if you're looking to compete within the next 12 months, I would keep trying to gain until you're about 5 months out from the show you want to do, and then begin a prep.