Start with HP&L to get you used to doing exams. Then do Air Law and RT Theory together as many items are common to both. Then do Met, Nav and Flt Perf & Planning before solo navigation leaving only Ac Gen & P of F and the RT practical to do before the solo 150nm navex.
PPL exams must be completed within a 12 month period, when you've successfully passed the final one you then have to complete the rest of your PPL within 24 months.