If it's only a 34L Tank I suggest paying ~$70 for a bag of flourish "nutrient rich" substrate from the shop, filling the tank to ~2inches, plant it well, then follow up with weekly water 50% changes and dry fertilizers (using Flourish liquid ferts = ridiculously expensive).
Dry fertilizers = powered form, you take a bit of tank water, mix up the appropriate amount and dump it back in the tank. There are calculators available freely on the internet that tell you how many t-spoons of powder to put in depending on water volume.
I would also invest in CO² (try DIY at first, google for instructions), and if you're serious buy a pressurised system.