Jimmy, it's not clear to me from your post if you were converting from a goldfish tank to tropical, or if the goldfish are still in there and you just plan to add a heater. If the goldfish have been evicted, okay, but goldies are coldwater fish and don't really belong in a tropicla (heated) tank. If I misunderstood, my apologies.
deffinatly get a few corys (6 at the least as there a schooling fish) theres a few different colours and patterns u can get but my favourite is the panda.there a brilliant community fish (which will probly be best for u as your new to tropical fish keeping) and clean up your tank a bit.
good luck and hope to see your new set up tank in the near future.