gcse advice

Start now and don't look back. Trust me, it will be worth it.

go through each topic through videos and textbooks and make notes?

Exactly this^. People probably tell you this everytime, but starting now will benefit you in the long run. Get your textbooks together, go through them, make notes, questions on topics you don't understand and just go from there. Small steps and then onto the big steps as the weeks go by.

I have mocks soon how do u suggest to approach them x
tysm xx

Go over past papers, watch YouTube videos and make flash cards on topics that require memory. Make sure you don't pack in too much revision, start light and slowly get into the routine of it- Good luck! X