it's best to talk to a careers adviser at school. i'd say if you're not one of those people that have always known they want to do a certain subject (like medicine) then choose a 3rd subject that will open as many doors as possible. i spent most of this year aiming for dentistry, so I took Bio and Chem, but then thanks to maths i'm able to now apply for computer science. If you're toying with the idea of economics, go onto the ucas website, type it in and check the subject requirements at any universities you're interested in. you'll want at least 2 universities that won't require maths (keep in mind you'll need to apply for 5 courses next year, so if you can't find that many economic courses that don't need maths, consider if you'll be able to find a similar course to apply for as well.). Find out how many doors english will open for you. What other grades did you achieve at gcse?