Subject choices help?! Urgent please

Okay, so Im gonna put it out there I basically failed my GCSEs due to laziness etc. Yeah I didn t feel bad but now I m set on fixing my mistakes (as much as or if I can) in the form of BTEC diplomas/certificates. I want to start college now and do some good subjects. I ve been recommend applied science from family members and BTEC Level 2 applied science extended diploma seems a good place to start. Am I right in saying that this is equivalent to GCSEs A-C? And could somebody clear up how many GCSEs that would be equivalent to if I good a good result. Would it be 3 as its biology chemistry and physics. By the way i totally flopped science and I got a D overall. (1 C grade :/) anyway would that be enough, the applied science level 2, or would I need to choose another subject alongside? By the way I m choosing 16-19 courses and I want to further my study (hopefully) to level 3. Would this be a good idea and can someone please clear up what else I could choose and what o can do with these qualifications in the future. If you read all that THANK YOU because I have no idea where else I m going to get answers from :/ x