It sounds as if you would most want to do maths, so I would focus on your maths gcse to achieve the 8 that you need. That being said it is your decision and you know what is right for you. Maybe have a look at the specifications for economics/politics to see if they interest you.
I’m not sure if this is possible in your school, but in my school most people do four subjects in year 12 and drop one in year 13, so that could keep your options open.
Also if you have a specific career or area that you want to go into have a look into the a level requirements to see if you would need any of those subjects. Maths would be useful if say for example, a science or science related subject is needed.