You have huge dreams that will not fit into your small tank. It's great that you are pursuing this hobby, but remember that the optimal health of your fish is true success. Crowding and overstocking = fail. And you cannot have an adult Oscar in a 55g. Not even one all by itself, unless you like doing 50% water changes more than twice a week to keep your nitrAtes below 20ppm. My O just passed 12" in his 125g and he just has room to pace.
Pbass is out if the question until you get up past the 200gal mark. Remember, base all your calculations on the average adult size of each species.
Try a breeding pair of severum for a really good time. Rams tend to be fragile and with you still learning to maintain your water parameters, it would just be a let down to watch ram after ram die. Severums are a little more forgiving than rams, and they are very slow growers. A 55g is a great tank for a pair of sevs, and watching them breed is like money in the bank.