Well just for some info, we have a little goldfish in a 5 gallon with filter, and I really wanted to be able to move that poor little guy in the big tank! So, I will keep in mind that I could possibly have up to 5 goldfish, however, I really want to have an exciting array and community. I was told by some that my little goldfish absolutely could not mingle with tropical fish, and then some have told me that the goldfish can be okay in a 75 degree tank with other fish....I am lost on that one. I would really like the goldfish I have to have a better tank, so any advice on whether he can be transfered or not will be helpful. If the answer is no, I am sure I would end up getting him a 10 gallon...
I suggest getting your goldfish at least a 20gallon tank. He will thank you for it and it will also be less stress on you trying to keep his tank clean.
It is advisable to put tropical and coldwater fish together. Goldfish are coldwater and don't require a heater. Tropical fish like warmer temps. and therefore need a heater to keep their temperatures constant and higher around 78F degrees.
Goldfish will tolerate these temperatures however they will not be happy and it will most certainly shorten their lifespan, which is not fair to the fish. So since you have one goldfish already, I would say you could only get 3 more Fancy goldfish at the most!!!
I am very much interested in having Angelfish. I know they are aggressive, but I like the challenge I will want to have atleast 6. So with that said, I know that I couldn't have small fish such as tetras. Would guppies be okay, or will the angelfish grow and eat them? And what are your suggestions of other fish that could go well with angelfish that would make my tank more exotic?
Guppies are similar in size to the angel fish and therefore I would not chance putting them in with the angels.
Article on Angelfish Take a look at that article, it explains the general information about Angelfish. I would also suggest posting in
New World Cichlids forum about your angelfish questions. More people will be able to help in there with setting up your tank for angels.

And combining other fish with them.
Now for a different presepective, if I decide on a different array of fish if I find that not too many types can live well with Angel Fish, I also love Gouramies, male guppies, zebra danios, burmese border botia, african chiclids, Platys, and also the freshwater stingray. Now don't get me wrong, I definitelt do NOT want to overpopulate my tank! I just want to have a nice enough variety of top, middle and bottom dwellers that would live happy and well with plenty of space. Is there any way you can tell me what of these can go together and add any species if you like!
Think of it this way when your adding fish to your tank. Find the total adult species size in inches for the fish you want. Then think of one inch of fish per gallon of water. So in the end you could have about 55 inches of fish in your 55gallon tank.
Take a look here at all the categories of fish and read up on a few that you think you may like.
I personally like swordtails, platies, zebra danios, neon tetras, corydoras and african dwarf frogs and the list goes on.
Good Luck deciding!!

Any more questions or thoughts feel free to ask away!!!!!
Another thing before you add fish, most people on here will tell you to do a
Fishless Cycle. It's all explained in the link above. And if you have more questions about that, feel free to post in tropical chat section of the forum.
I personally have never done fishless cycling, never even heard of it till joined the forum. And i've never had any problems not doing one before. I do things completly different then most memebers on here would i'm sure, but it has always worked for me so why change to something new, if the old way works great.