Have you tried sunbeds? Honestly, I can't give a load of advice, if you can't tan naturally you sort of have to use fake tan, or have you tried some tan drops, something like that, they're supposed to give you a warmer glow or something. If you just want to tan for prom then I'd say get a fake tan, I know someone who wants a tan for prom and they're going to like a proper place to get a full-body tan, so you could get it done professionally to look good for prom, but for every day, I think fake tan's your only option as you can't force your body to tan or anything