What should i feed these fish/plants?

You should feed them just regular tropical fish flakes, only give them as much as they can eat in 3-5 minutes. It's always better to underfeed than over feed, so make sure that if all the food isn't eaten in less than 5 minutes, feed them less next time. Also, make sure you only feed them once a day. You should NEVER clean a fish tank for any reason. There are bacteria that live in the water, on the gravel and all over inside the tank and if you clean the tank these bacteria will die and the "cycling" process will start all over. Pretty much, these bacteria turn the waist the fish produce from toxic chemicals to non toxic. If you don't know what cycling is, search "aquarium cycling" and read some articles, it's the most important thing someone who is just starting should know because without understanding this process you will likely have lots of problems and illness in your tank. As far as the type of gravel, I don't know exactly what to tell you. I have always used just regular gravel, but I don't keep many live plants either. If there is anything else I can help you with, feel free to email me if you don't get anything on here. I'm always happy to help and if I don't know that answer I will try to find out! Hope this helps and good luck :-)