People don't really feed their soft corals (they're generally photosynthetic and get most of what they need from the light). Having said that, there needs to be sufficient amount of light (what do you have for lighting?). Otherwise, like someone already said, they sometimes consume small particulate matter.
Soft Corals are not abbreviated like LPS or SPS
Substrate (sand, crushed coral, etc.) is a matter of preference. I prefer no substrate at all (bare bottom).
Tube worms, like featherdusters, generally seem to prefer medium random flow. They are filter feeders, so they definitely do prefer some flow, but not too much (they won't open if there's too much). This has been my experience, anyway.
Live rock, as already mentioned, is necessary for the biological filtration it provides. It's one thing you can't really skimp on (though some will argue that you can get by with much less than 1-1.5 lbs/gallon...and I might agree).
Good luck--read LOTS and keep asking questions