As
@Arricefe mentioned, soft corals are the way to go when starting out: mushrooms, green star polyps (GSP), xenia, zoanthids, leathers like toadstools and neon green sinularia are great as well. One thing to keep in mind, is that most of these soft corals (save for the leathers) can and will spread like wildfire. A lot of people say they regret putting GSP, xenia and/or mushrooms in their tanks as later on they're difficult to get rid of. Me personally, I like the way they look and the fact that they grow fast, so it doesn't really bother me.
Here are some pictures of several soft corals in my tank that I think look pretty good.
Yellow/Purple Zoanthids with a Ricordea Yuma Mushroom in the background.
A few "name brand" zoanthids including Sunny D's (front), Utter Chaos (middle) and Gorilla Nipples (back).
Mushroom garden (hairy mushrooms on top and watermelon mushrooms on the bottom).
Here's a side shot of my tank where you can see some GSP in the middle background (behind the clownfish), a toadstool leather up top and a few more mushrooms towards the bottom.
Let me know if you have any questions and I'd be happy to try and answer them. Welcome to the addiction!