If budget is of your main concern, then you have several options. One, use a DIY CO2 method, which might be a little challenging for a tank that size, but nevertheless provides a nice alternative to pressurized. You can search for all kinds of methods, but the one I found to be the most effective is one called 'Nyberg Method'. I don't know how many times I must've advocated it. Just give it a try. Two, you can skip the CO2 route if you just have plants that can do ok/well without it. Usually, those plants are also less light-demanding. You can find those plant choices in the Plant Finder section. Good day.
Paul
Paul