You can't take a PPL skills test unless you have the minimum of 45 hours flying training
Not true, you can take the skills test as long as you have the 25 hours dual and 10 hours solo, with 5 hours x/c, etc.. as long as your instructor is happy.
In terms of saving money at PPL level, if you can join a club with reasonable rates and voluntary instructors, you could well save yourself some money and save yourself the bother of a club checkout when you move on to experience building.
As Nibbler says, buy only what you need and when you need it. Also, clubs tend to have the books around somewhere, I know a few guys who never bought them, just studied in the club house on weekends, etc. And the more you hang around the airfield, helping out, making tea, the more offers you will get to fly as a passenger!