If you're looking to get into writing, I'd recommend doing whatever the hell you want. Write what you want and have fun with it. If you write something you don't like, it drains you. As for punctuation and stuff, honestly I've seen some awful grammar in amazing stories, as long as you make sure you've got the basics. If you want to go further though, definitely do learn correct grammar as it only improves the story. But yeah, find a thing you like (for me it was inflation) and just write your ideal story