You don't need no CO2 system for no planted tank that's BS; look at mine here click each link to enlarge these tanks non of them revives CO2 nor fertilizers and I'd wanna have to say the pictures speak for themselves.
What you need is proper light and that's daylights rated around 6500 Kelvin and NOT too much wattage (it will melt your plants if too high).
Easy care plants then I suggest to NOT go for stem plants as these will requite trimming and spec these small tanks you're better up with
Different colored Cryptocoryne; Java Fern, Anubias, Small Sword (eg KLeiner Bar Sword); Dwarf Sagettaria or Dwarf Harigrass or Narrowleaf chain sword
You can see all the named plants in my tanks or look them up individually here; may be worth while browsing through there and see what you LIKE as well www.sweetaquatics.com
All the named plants would do well in a 10g or smaller set up. The benefits of having plants will be amazing your fish will feel much mre secure as this is more natural to them and you will have a much better water quality for them as plants act like mini bio filters