I like Michael's list as well.

I'll note that umbrellas are considerably less costly than a good softbox and both are useful, if that's a concern. Look at the portraits of Timothy Greenfield-Sanders--almost all done with one umbrella, sometimes a fill reflector, sometimes with background lighting.

I started with seamless paper rather than muslin and still like it for most purposes. If you have a background light, one roll of medium grey seamless can be quite dark, neutral, or virtually white, depending on how much light you throw at it. A roll of super white, one medium grey, and one black will cover most situations.