What kind of plant you can add will depend on what kind of light you have. Do you have any information on the light your aquarium has, the bulb or wattage?
The bad news is that none of your fish can live in a 10 gallon for any length of time. Both
Goldfish will get to be 6" or larger. They produce too much waste and physically take up too much room to live in a 10 gallon tank. Conventional wisdom is 20 gallons at least for the first
Goldfish and 10 to 15 for each additional gold fish. You also need a powerful filter to handle them. Finally gold fish are cold water fish and prefer temperatures in the high 60's to low 70's, the angels are tropicals who prefer temps in the high 70's.The angelfish are also not going to be able to live in the tank long term. They are going to grow and their fins will stretch from the substrate to the water's surface. Angelfish need to be kept in tall tanks so they can have room to swim. None of your fish will be able to stay in the tank.
There are quite a few fish that can be kept in the ten gallon though, a ten gallon could support a good school of tetras or rasboras, shrimp, platys or guppies. If you have questions about those please ask.