If you haven't made many bows, I'd say shoot for 70# at your drawlength. After a couple hundred bows I still shoot for at least 10 lbs higher than what I want. Let's just say I've made plenty of "kids" bows unintentionally.
If you get 'er tillered in heavier than you want, you can still gently scrape to a weight you can handle. Putting it back on is a bit more problematic.
As far as deciding what you want for a final draw weight, you will have to consider what you want thr bow to do. I have shot 50# bows for years and decided I want to push that up to 60 for a little flatter shooting for hunting. I'm not saying you can't hunt with a lighter weight bow, one of my 32# kid's bows harvested a whitetail doe a few years ago (I didn't do it, I'm too afraid of wounding and losing an animal). If you want a good roving or plinking bow 40# is easier to shoot all day long.