Working in conjunction with your instructor, start with an outline ground school plan and some idea of timescales. Much of the information that needs to be considered can be found in our learn to fly guide and Ground School Introduction. To a large extent, the plan will be driven by:
Everybody learns differently, some people can just read hundreds of pages and absorb it all, some people need to understand it, some need to visualise it and look at the practical side, some people respond well to classroom environments and working in a team atmosphere, some like videos... The point is, everybody is different and this must be taken into account in any structured learning program and plan. The 6-sitting requirement was removed in Oct 2019, it is now possible to study the nine PPL ground subjects one at a time, sit the examination and then move onto the next subject (the only real exception to this is Navigation / Flight Performance and Planning because the subjects overlap on the chart-work and planning).
For each subject, PPLmentor has divided them into Topics, these are taken as-is from EASA FCL (the 1400 page document that specifies exactly what the ground school must comprise of). These EASA topics are further sub-divided into the EASA sub-topics to create a logical learning program. Where it is possible and sensible, the sub-topics reflect the chapter groupings in the Pooleys Air Pilot Manuals. The PPLmentor Structured Learning Program is based around become proficient in each of these sub-topics one at a time by:
Sometimes, this may not work (especially with Meteorology) and any structured learning program will need to consider this eventuality. The first port of call is your instructor who will undoubtedly gain assistance from the head of ground school training who in turn may well point you in the direction of a specialist who may be able to use a different approach and outlook.
You have 18 months to pass the examinations (starting on your first attempt, not first pass). Providing you have the dedication and time, use all the resources available and apply a structured learning program, it should not be an insurmountable challenge.