Algebra, Calculus, Algebra, Caluclus, Algebra Calculus. you get the gist I hope
Most of the time when you can't do a question is because you're eitehr stuck on algebra or made a mistake with your differentiation.
solving and factorizing polynomials (esp quadratics)
typical expansions (difference of squares cubes etc etc)
Trig identities VERY IMPORTANT
Understand and apply differentiation rules, especially the chain rule (function of a function)
The you brief through the concepts.... Geometry is a bit annoying . also probability. It's more practice for these topics.
Coordinate geometry (locus etc) is easy once you got your algebra and calculus straight. only things you should need to remember from those sections are:
distance (just's pythagoras' theorem)
gradient
formula of line given point and slope or 2 points.
midpoint
division in general ratios
Changing quadratics to standard form for parabola.
Further apps of calculus.. if you have the basics right, this should be easy section. go through SHM, and the ways to express acceleration.
Practice papers are good for refining your exam techniques and boosting confidence, but save that after learning from the textbook.