If you are just starting out. Try to avoid getting plants at first. Put all your efforts towards the Discus and their care above all else. Learn to satisfy the discus needs and care first. Many times you are starting out with small discus fish and it may seem that every thing looks and goes well in the beginning. Remember the fish grow and will produde more waste as they get larger. This will help you to maximize your efforts with the fish.
Bare bottom tanks are easy to take care of and maintain, but not much to look at. They do offer a cleaner tank above all other types. You could try to have a few plants inside a flower pot to see how you will do with both plants and Discus together. This allows you to move the plants around for easy cleaning. You might also look into some of the new types of artificial plants or driftwood to decorate your tank. Something that you can take out and clean easily.
A gravel bottom type of tank might be more pleasing to the eye. Although they require much more effort on your part to maintain because this type of tank you will have to vacume the gravel on a regular basis. Although you can never get the gravel clean enough. Either way you choose, it's up to you.
With an all Discus tank you can put all your efforts towards the Discus. With a community tank you can get side tracked with other types of fish. Compatibility problems with discus will be one concern you will have. Many people keep discus in a community type of tank. The choice is yours on which way to go. I personally feel you will have more enjoyment along with a better chance at success with the fish in the long run with an all Discus bare bottom type of tank. Simply because you eliminate so many other possible problems with introducing plants, different species of fish and the ability to see how much unwanted debris collects inside the tank.
A general water quantity for keeping discus would be about 40 L/Fish. This could be more depending on if there are other fish kept with the dicus.