Looks alright for a first build. With every part you make, there'll be different techniques. I usually have to make a single part 2-3 times before I'm happy with it. You can also experiment with different ways to fill cracks and seems, so eventually you have a part you're really proud of. The recommendation for thinner foam is more important on a helmet than other parts, but you can still have great results with the thicker foam, just trickier to do.
Keep it up and don't be afraid to redo parts prior to doing the finishing work if you're not satisfied. Good luck!