Lighting can be confusing. Fortunately, many TPT members have already been there, done that AND made notes! If you go to the lighting section of the forum and look at the sticky posts, a bit of a reading there will go a long ways.
For a summary, you need to determine the PAR levels that the plants will see at substrate level. This is a function of the type of light, the light's output, and the distance between the substrate and the light. LED fixtures are now fairly affordable and I'm confident that you can find one for your tank for roughly $100. The LED sticky thread in the lighting section has PAR levels for many, if not most, of the major/common LED fixtures. Simply figure out which fixture can fit over your tank (based on how long your tank is), look for that fixture on the thread and it'll give you corresponding PAR levels at various heights. For LEDs, low light is anything below 30 PAR (at substrate). Medium is roughly 30-80 PAR and anything over that is high light. You may find that you need a fixture with lower output, or, you may simply raise the fixture to increase the height between it and substrate level.
CO2 is not necessary at low light and even many points within medium light but it will help nearly any tank. Medium light is iffy without CO2 as you can find yourself with an algae explosion quickly - especially if you're not heavily planted.
Hope this helps you get started!