Good subjects for Economics at top 5

Yep, sounds good. You've got M+FM and two other academic subjects, you're all set. Just make sure you show your commitment to econ through your PS and try to do something like work experience if you can or just read a few books. Be aware though, econ is one of the most competitive subjects so even incredibly good candidates don't always get offers. So you'll need very good grades. Best of luck!