I used patterns from this website. It was my first time sewing something bigger. I didn't really find any more detailed instructions as to how to sew everything together, so I was doing it somewhat blindly.
The most trouble caused me the belt part. I had no idea how to sew it. I tried adding belt loops and straps, but the results weren't satisfying. In the end, I put in elastic rubber band. It helped a lot, but because I wasn't planning on adding it on the beginning, it is how it is.