we all start as beginners but you did an outstanding job anyway you look at it. I love the little blocks, I just don't have that much patients to do them.
As for how to finish it off, I would add 1 or 2 more rounds of blocks around the out side just to give room so as not to cover the outer stars, then pick a backing that blends well with the front. Sandwich it up and roll the backing over the front edges as a binding.
When I use this method, I cut the backing 1 1/2 inches larger then the top. Then fold that in half, then roll it over the front edges. It should end up about a 3/4 inch binding and you can sew it down on your machine with little effort.