What sort of look are you going for with your tank?
Softies are the easiest, they don't need pristine water and they don't use up much of the big 3 so weekly water changes are all you need to keep parameters stable. However, there are many different types. Do you want something that hugs the rocks and grows out not up? If so I would pick things like Zoas, mushrooms, GSP(green start polyps). This will give you good rock coverage but not a lot of height. If you are looking for things that grow up and out I would suggest Toadstools or Leathers. One thing about softies, they like to use chemical warfare on each other so I like to have a bag of carbon in the sump