Tiger Barbs are native to parts of south east asia where frankly 90% of all plants and fish come from that are popular in the hobby. I might be exaggerating a bit with that 90% figure but it sure feels that way. Anyway the easiest root feeding plant of them all are various types of cryptocoryne which are native to south east asia. You could go to your local fish store and pick out some crypts. Put in some drift wood and some rocks. Bank the sand to be higher in the back and off to one side and you have yourself a lovely easy to put together aquascape. Watch some videos on youtube on how to prepare plants, it will be a big help. Somebody like George Farmer works with a lot of crypts and has a ton of good quality videos out there. He tends towards high tech scapes but you can still get a lot of valuable information from him.
Pool Filter Sand is a nice (and cheap) substrate option. Smaller gravel sizes (1-3mm being ideal) are also a good choice. You could go with root tabs but its easier and frankly safer to get an easy liquid fertilizer. Thrive C is often recommended for low tech planted tanks because it has everything you need in it including liquid carbon.
For a light there are a lot of options here. Crypts are low light plants so you don't need a lot. Beamworks lights get a lot of attention because they are cheap. They are better for low light to maybe the lower end of medium light. You can find them on amazon. A more expensive option would be something like a Fluval 3.0. Both will grow crypts in a 40 breeder. The Fluval will give you more options down the road if you decide to go high tech. Read up on them and you can make a decision.