the answer will depend on a lot of factors. Youve already said you are low tech--so that rules out HC and some of the other higher light plants. However, it would allow you to use Crypt parva or lucens depending on the size of your tank. They grow slow and steady and look nice. Another option would be Stauro. porto velho. I am currently growing a carpet in my 29 with it and love the looks. It grows fast and agressively with good lights, co2 and ferts---slower and more managable with low tech setups. You could try Stauro. repens/049 but I havent had any luck with it in a non CO2 tank--YMMV.
If I were doing a low tech tank I would go with dwarf sag or Crypt parva if it were less than a 40 gallon tank and Stauro porto velho or Crypt lucens in a larger tank.
I never liked E. tennelus because it would grow on top of the substrate almost as much as it grew IN the substrate.