If you're using potting soil already and don't need to buy any more, you could just get a box of the fertilizer and larger buckets. There are other options, like sticking with that soil you have and getting a small bottle of dynagro fert at the hydro shop. It has pretty much everything plants need to grow right. One half teaspoon in a gallon of water is all you need of the fert. If you can't find the pint sized bottle you'd have no choice but to get the bigger one, which is kind of expensive. Chances are good you won't used all of it because you need so little to get the job done. You don't need to spend much money, just enough to get things done. For alot of people getting the box of fert I mentioned earlier is better cuz then you just add water. Don't get talked into anything else cuz it's not necessary.