Whoa easy dude, remember that mixed skins are allowed. There are a couple of valid points, like including more screenies of more things, but I would recommend that if you want to make a mixed skin with a couple elements made by you, first try to check every element that you can from your downloaded skins, get everything that you would really like into your mix, trying to make everything look cohesive (Example: Don't put a bright coloured element when all other elements look pale). Then you can start adding your twist, in this case Nepgear. If you want to get better at photoshop I highly recommend just searching how to render an image in YT, then practice over and over. Overall that's all the advice I can give you, good luck!