I havnt had great experience with online. But here are some super easy corals.
Palys
Duncan
Leathers
Mushrooms
Galaxia
Most lps
Montipora
In my experience......:-)
Legendary corals is great but they deal in high end collectors pieces. Not bad if you can catch a live sale like they have right now but otherwise a bit pricey for the beginner. I will be honest somehow someway you will loose a coral during your reefkeeping career. Wiz has a good list going. All of those if they are not priced super high are going to be tough and grow good for you. I recommend getting corals from others on the site. Most would be glad to help and these corals are used to captivity.
I have from uniquecoral.com and have had a great experience (Zoa, and Xenia with a few others). Have also got some from Saltwaterfish.com (frag packs) which ended up a 50/50.
Question I'm wondering is if anyone has any idea about limits on how much coral you should or could put in a tank. Fish you have the inch/gal limits but I have never found anything about coral limits.