Its four sitting per yr now so if you want to be successful and pass withing 2 yrs one P paper per sitting should do it. The order you do it in is up to you. I would suggest to schedule P2 and if taking P5 the time of yr when you have more time to devote to studying e.g. tax time is a busy time for some of us so i wouldn’t suggest tackling the hardest papers at that time.