I think one of the best items to get is a pair of quality enclosed umbrellas like the Lastolite Umbrella Box. These keep spill light to a minimum,since they are enclosed and the backs are totally opaque black fabric. Lighting is 'similar' to a softbox, but easier and faster for a beginner to set up,and very easy to transport/store. This is a reflecting umbrella design, with a white, zippered cover that closes tightly around the flash head,and offers very nice light quality. A similar umbrella design is that of the Photek Softlighter that Annie Liebovitz has been using the last few years.
Lastolite Limited, Manufacturer of Umbrella Boxes and Studio Equipment.
SOFTLIGHTER II
A second item that I think is very,very handy is a 7 to 11.5 inch reflector that has the ability to accept a 20 to 35 degree honeycomb grid AND a set of 2- or 4-way barn doors. Another honeycomb grid that is exceptionally useful is a 10 degree grid; I think a honeycomb grid set is vastly more useful than a snoot. Snoots are not nearly as useful as grids, in my experience.
If you buy a softbox, try and get one that has both a recessed face AND a set of louvres or "egg crates" that fit on the front,and which help control the direction and spill of the light emanating from a softbox.
Cheap, white $15-$25 "shoot-through" umbrellas cause a LOT of spill light to bounce all around your shooting area,and make it much harder to understand the effects of positioning lights. I learned with shoot-through ubrellas,and found that with ample watt-seconds sent through one, it would not only provide main light, but also a fill light effect due to all the light that bounced off the back side and as blasted all around the shooting area. If you have to shoot in a low-ceilinged room (basement,apartment,small office) the cheap shoot-through umbellas often produce very ugly,dull, vague lighting effects,and that is why I am specifying two *quality* enclosed umbrellas, the Lastolite Umbrella Box,and the Photek Softlighter. There are cheaper knock-offs,and also another type that does not reflect and then diffuse the light, but which is just a shoot-through umbrella with a back cover on it....not quite the same thing as the two genuine unbrella boxes I am suggesting.
I do not use Alien Bee studio flash, but another brand; if I were just beginning and wanted to use just umbrellas, I would look a the
Adorama photo store's Flashpoint II monolights as a lower-cost option,and would buy three or four of their 320 models. See this URL
Monolight Outfits
I would also look at the Flashpoint's 16-inch "beauty dish" parabolic reflector as a very useful type of light modifier to buy.
Keep in mind that the Alien Bee "400" is a 160 watt-second model and the Flashpoint 320 is a 150-watt-second model. Both are amply powerful.
I've watched the Alien Bee crowd grow in strength over the years,and almost to a person they will discount any other brand of lighting. I do not own either AB or Flashpoints,and have no dog in the fight--but I would rather own two lights of about equal power for the price of one light,and would really much rather have four lights than two lights. As a user of another,entirely different studio flash system,to me the Flashpoint monolights appear to be more what I would suggest to somebody who wants to get into studio lighting on a small scale without paying too much money for lights that so many users seem to have to send back for warranty repairs.