Get the biggest tank you can and dont crowd it. Smaller tanks are harder to keep the water chemistry good. Let it settle for at least a week, more if you can and add the fish slowly, one species at a time per week I think is safe. Change 20-25% of the water every week, twice a week if u can, for the first month or 2. By doing all this you should hopefully b able to keep all the ammonia and crap down and keep your fish healthy.
If you buy a new filter I have a tip: fill a bucket with water and run the filter in the bucket for a few hours. I have placed brand new filters in tanks before and it can contaminate the water with plastic or something and kill the fish.
If you know someone else with an established freshwater tropical tank ask if you can wring their filter medium out into your new filter(after the bucket). This will help introduce the good bacteria needed to keep the chemical balance right. Also see if you can take a bucket of their filthy water to put into your tank, this will also help out a lot. As long as their water is good and their fish are healthy. Best if they have a planted tank too I think.
Plants are tricky, but the two plants you want should b fine, Anubias and corkscrew val. I have found in smaller tanks it is best to have one or two species only. This way you can get away with not using co2 or anything too extreme. I do recommend using some form of liquid fertiliser in this instance, it will help dramaticaly. Weekly or daily doses. Probably weekly for easy maintenance and to avoid algae. If you do get algae growth slow down the fertiliser and turn the light on for less hours. Put your light on a timer also to give the plants a normal days light every day.
That is about as basic as you can get for a decent small planted tank. My g/f has one like this and it is fine, her plants grow and her fish are happy. I think it is 20G. She has a few platies, couple of cory's, couple of khulis and a betta.
Good luck with it.