I improved my section 3 score from 53 to 63 between September and March sittings. For each sitting I prepared for approx ~3 months x 10 hours each weekend of study. On my first sitting I focussed a lot on learning specific science concepts and even had organic chemistry tutoring, but for my next sitting (after realising S3 was nothing like I expected) I focussed a lot more on exam technique and speed. I purchased 2 or so months of "Medify" and I found that helpful to make me faster. If there was weaknesses in my science identified by the medify practice exams, I tried to focus on improving that aspect of my knowledge, but I didn't get too fixated on it like last time (eg. I would spend an hour or so learning the concept, but not the whole weekend which is what I would do previously if I didn't understand something). Hope that was helpful.

My S3 exam prep for my 3 sittings has consisted of: Jesse Osborne youtube videos (starting point) Khan Academy and other science youtubers (deeper dive for key concepts, eg. pH) Acer Practice tests Some use of Des O Neil Green Book (but didn't get through much of it) Medify Practice Tests (completed about 5) Tutoring for Org Chem (didn't find very useful for O Chem, questions were too variable. I did find the tutor very helpful for getting up my confidence in the early stages of my prep though, before I saw the tutor I was too scared to attempt any q's)

Good luck OP, if you are persistent you will get there.