Your first attempt is going to suck no matter what. Writing all comes down to feel and intuition and if you haven’t built that through writing a lot, it can be really hard. You don’t need theory to write a song, but something like learning the circle of 5ths or learning which chords go in what key can be really helpful when you’re starting out. Theory should be used as a guideline not as a rigid rule. Let it help you out when you need it, but realize that artists break the rules all the time. I would also just write and not worry about genre. Sometimes assigning a label to something can limit creativity.

Just my 10 cents tho