There are a variety of ways of hour building and each probably depends on your circumstances. For me its purely financial so the cheaper the better and probably the cheapest way of doing the hour building segment is getting involved with a group run aircraft. PFA is usually the most cost effective. For example the group Im involved with is £30pm to cover hangarage and maintenance and then we just pay for the fuel we use (about £10ph).
Of course when you come to do your CPL training you probably want to have a bit of experience in something which is a bit less basic, so it might be worth budgeting for a block of hours in 152/172 to get your general handling up to speed on that type of aircraft.
A word of caution though, when you have found what you think is a suitable group aircraft, give as much attention to how the group is run as to how suitable the aircraft is!!