Starting C02 and ferts from day one is recommended by most people. If your going for a low light tank then using Seachem Excel will work just fine, however injected C02 is always best.
The main thing to look for in choosing plants for a Goldfish tank is growth rate and sturdiness. So in other words fast growing plants (Anacharis) and thick plants (Anubias) will work best.
Here are some sites that will help with your selection...
http://www.well.com/~debunix/fish/goldfishPlants.html http://www.kokosgoldfish.com/Plants.html