Honestly, dude, you’re being so vague it’s hard to really help you. “Good” drums is subjective, what you mean by good could be over-compressed and “bad” to another person. Good drums to me are really simple and small. Mastering is relatively simple if you mix well, because if you’re mixing isn’t insane all you’ll really need is gentle compression and some minor limiting. I get that you’re going for the atypical Skrillex sound, so you’ll probably be tempted to over-limit and over-compress but I guarantee less is more with those tools. Making melodies is in part about messing around, and there are plenty of other threads about melodies if I’m not mistaken. But beyond that, I don’t know how I can help you.
Edit: I was mistaken about there being a melodies thread, but there is a “how to make good chords” thread, and some of the lessons apply to melodies as well How can I make good chords?