A few points from my experience.
Firstly, go with the Trvor Thom books. I have volume one (ppl course) and the detail is superb. Nothing is missed out. I got this as part of an intro pack from my school.
Then I went and did something silly, and bought the rest of the course manuals in Jeremy Pratt. Don't get me wrong, he does explain things well, but appears to concentrate on humour rarther than a complete explanation of the topic. Come the day of your air law exam you will go through it thinking... now where was that in the book? I did.
For example, one of my air law questions was about what material should the aircraft id plate be made of? (something like that). The correct answer is fireproof metal. I couldn't find any reference to that in a Pratt book, and only knew the answer from working in a related industry.
As for the all together packs, they do show a good cost saving against buying it all seperate, but then again, it is a chunk of money all at one go, money that could be spent in the air. I have been learning for a year now ( just gone first solo) and have only just bought the nav tools.
I would recommend that first of all, you buy Thom Vol1, a headset (Pratt does say that there are several hundred ear related infections available from a shared headset), a knee board and paper, a good pair of sunglasses, and an air law book. That will do you until you are getting somewhere near first solo. Remember that that wont happen over night, the average is 15 hours so I'm told, I took 22 as I was weathered off a lot of lessons in November and December, and had to get the hang of it again!
Save the rest of your money to either go flying with, or to pay the rarther large doctors fee for your medical. Set yourself a goal ( mine was first solo) and take it from there. New editions of books come out every year, so all the complete set I bought last year are now probably out of date. I will get by as I have done air law, but I do wish that I had waited until I needed each one.
And finally, on topic of ground exams, don't forget that there are time limits for taking the exams, so don't be in a rush to take them, wait until your instructor tells you that you are nearly ready for solo until you start with air law. Nothing wrong in reading up on the topic, that would be sensible, but a bit like pringles, once you start, you can't stop!
All that negativity aside, this is a great pastime, and the feeling associated with it are wonderful. I wouldn't do anthing else!!!
One last piece of advice, I have book at home that I bought years ago, called "the funny side of Flying" by a great pilot and writer called Alan Bramson, it is a book of jokes and observations and indeed is very funny. In one part there is a statement that I always take into the air with me " even amateur pilots have to act like professionals, if they want to grow grey hair"
Good luck!