A lot of people who have complete "non-budgeted" tanks dont have the high 3-4 watts per gallon (which is somewhat antiquated anyways) that is "required" for high end plants. Its more about meeting the plants in the middle.
If you have good substrate, good co2, and quality light, you dont need as much of any one single component. Many people with the HO bulbs are using 2-3 wpg without any problems, and dense fast growth.
That being said with you wanting to save money...I dont know what we are going to do. Its best to have co2. It just is. There are some problems associated with it, and it has a start up cost, but no matter what happens you are going to want it sooner or later in your planted tank. Might be better to save a little money for some fixtures and a co2 system, and then set up your system when you are fully ready.