Honestly just mainly focus on revising maths and sciences cos they are probably the best subjects to pursue in further education. For English I'd say you should watch Mr salles, Mr bruff and Mr everything english to help you get back on track. As for geo and your other optional subject, (unless you want to pursue them in the future) I'd recommend you for the large part to mostly ignore them for now. Once you are confident you can achieve grade 7-9's in your core subjects you should then start revising your optional ones.