Personal Opinions: Almost all of the following personal opinion, but there is some emprical data referenced from J.P.'s video.
I do not, at all, subscribe to the idea that a 32 inch umbrella is only useful for head and shoulder shots...that's largely a myth, predicated on the idea of soft, mushy light, spewed in the general direction of the subject. Again...this idea that the light souce needs to approximate the physical size of the subject: that is an idea that has spread like wildfire since the internet got going, and it assumes that what you want is flat, even, low-ratio lighting, with little direction, and very little modeling of shapes. This 1990's look in lighting is passe.
There is a reason the 20-inch and 22-inch beauty dishes have become popular within the past 10 years: people have grown tired of 1990's lighting styles and lighting with massive modifiers as "big as the subject is". Sixty-inch umbrellas are a massive pain in the a$$ unless you have a full-fledged, vaulted ceiling studio to work with, and in many situations, they force you to have the light well below the subject's head level. The new 7-foot umbrellas? I bought one. Been used TWICE. Umbrellas in the 30 to 45 inch range are very useful, and as the video actually shows...they cover a BIG area, no matter what the size of the umbrella actually is.
Check this video and see for yourself:
This is the best YouTube umbrella tutorial I have seen. Take a look at the 2:00 mark and see that a Photoflex 30-inch reflecting umbrella loses 1/2 stop of light--over a 12-foot-wide area... So much for internet folklore. Across a 6-foot wide swath, the same 30 inch umbrella has only 1/4 EV of fall-off...assuming absolutely ZERO fill-light AND shot in a cavernous studio where there will be no help from any nearby walls or floors.
For the beginner, it's more important to learn where, exactly, to place the source or the light, and to have some shadows, some modeling of the subjects, to literally be able to see what the heck the light's placement actually creates; this is why I suggested the smaller, 32-inch umbrella size to start, especially with a speedlight.
The above Photek Softlighter II is popular with Annie Liebowitz of Rolling Stone; there are others similar, like the Lastolite Umbrella Box (which has the desired dull-finished vinyl interior) for VERY soft, diffused lighting; and also, $35 or so made in China umbrella boxes from Steve Kaeser Enterprises, and other vendors. I do not call these brollies. These are all reflecting-type umbrellas, with a front diffusing panel, so the light is doubly-diffused. Light leaves flash, hits umbrella concave side and is scrambled, then that light goes out through the front diffusing panel.