Well, mushrooms are a good start. The next on the list is just as easy, only a little more expensive. Your colt is a great idea. A toadstool, palys, a cabbage leather, and some bland colored zoas.
All of those should do just fine if your mushrooms did ok.
Acropora is a way more sensative coral, and you'd really wanna work your way up to that via softies, which your doing, then LPS's then easy sps's THEN the acros. Since they can be pretty pricey, your really taking a risk jumping straight to those.
All softies are easy to frag...again, pending what tools you have.
A colt coral only needs a simple pair of scissors that you don't mind getting saltwater on.
Shrooms are fraggable with a flathead screwdriver.
Zoas are tougher but I let them spread onto terricotta or porcelain tiled and I razor them right off since it's a smooth surface.
Toadstool and cabbage...scissors also.