How to have curly hair without heat braiding or rollers?

Hi, am in my teens, and sexy curls seem to be in right now. So, I have tried braiding (well actually I plait, I cant braid) and it just makes my hair wavy. My hair straightener is EXTREMELY wide and thick, so I cant use heat, and my mum wont buy me rollers. So how can I achieve the curly look? Also scrunching never works for me. My hair is quite layered and just past my shoulders. Thank you In advance.