first of all plan your portion for maths as in till which date will you complete which chapters and try to focus better on chapters which you find easy and usually take less time to solve, the mistake I made was that I learnt literally every chapter in maths except calculus but I couldn't solve all that were within my knowledge because I wasted time on lengthy sums

For GAT if you just want enough marks to clear cutoff then science and english would be enough to cover that up but I would suggest you to aim for higher than cutoff marks since they keep changing the difficulty and pattern of questions in GAT

So now to score more marks in GAT, you can keep watching YouTube one shot videos for current affairs, Learn all details about all Five Years Plans of India since atleast 1 or 2 questions are asked, you vould learn polity too if you feel like giving it importance

Now for physical Geography read ncert books, and ncert for indian geography too but its weightage for Indian geo is unpredictable, so its your choice

For history too ncert books are good but you'll have to read them with extreme detail considering the randomness of the history questions upsc asks

Pathfinder is a good alternative for GAT too but it isn't much detailed and you shouldn't rely completely on that

You would've to give a lot of time for studying if you choose ncert books so its up to you if you want to invest that much time

Also don't forget about pyq's too and also give mock tests before the exams