As you say, ya gotta start somewhere. Seems like you have a pretty good idea of where you were wanting to go with this.
I think if you look at the pictures you can see some stuff that can be improved. An easy one to spot is the uneven edge on the front. That's mostly something you accomplish by taking the time and care to do it carefully.
Pig skin is pretty thin for a mag holder. If you decide to do another, you might want to look at something a bit thicker that will hold it's shape.
Glue only works for so long. Picture leather as if it was a sponge. When you glue it, you're only getting the surface attached. Rivets, lacing, or stitching will give strength to pieces joined together.
Listen, there are 3 very important keys to becoming good at doing just about anything, including leatherworking:
1. Try. If you don't actually try to do it, you'll never know what you can accomplish. Sounds simple, but you'd be amazed how many people never try to do something they always wanted to do.
2. Look at what you've done and what others have done so that you can learn and try to improve the next one. If you can't figure it out, find someone who knows and ask them. Again, you'd be amazed at how many people never ask a question.
3. Start back at #1.