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Just have fun with it. When it comes to seeing truly competitive players, you'll see everyone using virtually the same mons. If you don't mind that aspect and just want to win, just watch vids on youtube.
I myself am catching/breeding competitive shiny versions of my favorite mons, and I'm sure I'll do quite well when I start playing online more. This route has you thinking for yourself while also utilizing the internet for the recommended movesets/natures/etc. Come up with something new, idk. Just enjoy it.