If I were you, I'd ditch the fruit salad gravel and go to the nearest beach and get some clean sand. Beach sand has ground-up shell in it, which provides your plants with magnesium and calcium. The best part about it though is that it's free and you can take as much as you want! CO2 is a good idea too, and DIY would work very well for a tank that size. Fish - well, maybe not Pearl Gouramis, they might jump. The only reason I think so is they are an anabantoid, and I had a fighter which jumped through a tiny gap once. I would be thinking more along the lines of small tetras, small loaches (Zodiac and/or Khuli loaches), or a large school of Mossie rasboras and some Emerald Dwarf Danios. A pair Apistogrammas and/or Rams is a must. Some more plants other than val would look good too. Small bits of bogwood are a must because they soften the water which the fish love (unless your getting hardwater fish).