Mushrooms are nice but they spread like crazy!! So beware. If you want some nice, but, more expensive softies, Ricordea Yumas are nice and have great colour. They are a lot more peaceful in a tank and don't spread as quickly.
I used to have a beautiful fluorescent Green Umbrella Leather. They are very nice and fascinating how they expand and contract. They get quite large but are very nice additions. Whisker corals are also very cool and easy to keep. Zoas can thrive but they can also be very tricky. Some will grow like crazy and others can melt away. Be careful of palys. There are some nice ones but they also can take over a tank very quickly.
Pulsing Xenia is another nice softie. However, same thing... They look great but can take over fast. Green Star Polyps are another one as well. Very nice bright green but make sure you have them on a rock that is not touching any other rocks because it spreads like wild fire.