If you are hoping to own beautiful adult discus in the end, I would suggest you get them from your local breeders instead of your petstores. You never know where the petstores get their stocks and most of their stocks are culled specimens which are not worth your time and money. Discus should not come cheap. Look at the extra efforts done to make them almost show quality which is the whole point of buying them.
Adult discus (4 inches and more in body diameter minus the tail) are less forgiving to water conditions than young ones. If you insist rearing young ones, get a group of at least 4 young discus and if you want to see them in their best potential, start with a barebottom setup and be prepared to do plenty of feedings and water changes. I am sorry to say this but buying a single discus will not guarantee you the best experience that you wanted. Moreover, unlike other tropical fish, keeping discus entails a lot of responsibility, patience and research on your part. Unless you are prepared to do this, then discus may not be for you at all even though they are not really difficult to keep contrary to popular beliefs and hearsays.