Pick any substrate you like the look of, I would stay away from the "planted tank" substrates, they aren't anything special, especially for a low tech setup. ADA Aquasoil "style" substrates are worth the money, but they aren't really for a low tech tank. More so suited for shrimp keepers, people with RO water and aquascape artists.
Black blasting sand, pool filter sand, silica sand, quarts sand, small grained inert aquarium gravel.... They will all work equally well. I wouldn't do a dirted setup, too messy and too many uncertainties for "beginners".
For lights you could use a beamswork DA_FSPEC (although it might be a little much for a 20 Long.... how are you with DIY splicing in a dimmer?)
2 x T8 shop lamps would work, fluval 2.0 or 3.0, finnex 24/7, current satellite, 1 x T5-HO, 4 or 6 13 or 23 watt CFL desk lamps should work for lighting. Budget is the biggest determining factor on lights.
Fertilizer are a must, cheapest and easiest are dry ferts.
GLA or amazon should sell these:
KNO3 - for Nitrate and Potassium
KH2PO4 - for Phosphate and Potassium
CSM+B - for Micro's
Pick up some flourish comprehensive too for a second source of micros (many in CSM+B are not plant available at certain pH's).
Check out rotalabutterfly and their nutrient calculator. They offer rates + amounts + various dosing regimes. (I highly recommend using a consistent dosing + water change regime).
Any filters should work, you'll want decent flow but not overwhelming (plants bending over from flow).
For easy going plants check out:
Any crypt species
Any sagitteria species
Pygmy chain sword
Rotala rotundipholia
Ludwigia repens
Bacopa
Helanthium
Java ferns
Anubias
java / christmas / fissidens / flame moss
Hope this helps....