Well since it will be my first time, I have no clue on efficiency. Also I ordered my grains and requested them milled, I dont have a way to do it any finer once they arrive, so I am at the mercy of how they are sent to me. Not sure if that will be an issue or not.
You're going to produce beer. It will taste good. It may not be exactly what you expected in terms of efficiency or gravity, but so what? You'll see what you end up with, and while drinking it you'll ponder what if anything you might change in the process.
One thing I've been struck by as I went from a beginning brewer to whatever I am now is how resilient the process is. It really is. So if your pre-boil gravity is, say, 1.050, that's fine. So is 1.044. And 1.053. As you boil down that gravity will rise (less water, same amount of sugar in the wort). So check that.
I don't know if anyone who brews extract checks their pre-boil gravity, not even sure how you'd do that unless you checked after all fermentables have been stirred in and right at the start of the boil.
But you should do that--check gravity at the start of the boil. Then of course afterwards. You'll see the gravity rise, and you'll have a better sense of how that crush works for you.