Hi Debj! Welcome to FishLore.
Congrats on the recent tank. Tetras, including the rummy nose, neons, and hatchets live longer happier lives in schools of at least 6. Imho, choose fewer types of tetras so you can have more in each school. Cory cats similarly prefer schools. In order to get the school numbers, you may need to limit the types in the tank.
Two
DG in a 55g makes me nervous. They're so darn territorial and it seems that many people have had aggression issues with them together, even in a 55g. I would really suggest just one, but others may feel differently on that one.
Best wishes to you and your fishies. I can't wait to see what you decide - others will be by soon with loads of good advice, too.
EDIT: OH! You've already stocked with all of these.... Hmmmmm...