Quite a lot of managers prefer to play with a young squad, simply because of the faster training rates, so what your doing is quite good, but what players you can buy is simply determined by the market on offer... If your on a older server which often has 5* players for sale then I wouldn't waste my time bidding on 3* players for example. I'd take a moment reading through the guides to help you get a better idea of playing the game and avoid falling into some "noob" traps early in the game like I did.