It's all shapes & patterns. Once you know them, you just know them. There's definitely things that throw me sometimes, but on the whole, I've picked up a lot of perfectly useful, useless knowledge, lol.
But being so new to collecting, I already feel a sense of being "priced out" of many wonderful vintage items - particularly the 1940's era stuff that I am the most drawn to of all.
Collectibles books only highlight this sense of frustration, with their wonderful pictures and descriptions of canisters sets, mixing bowls, range sets with shakers & matching grease jars. Wonderfully whimsical patterns (who knew Roosters could be so dang cute?). Interesting color names and choices (Chalaine blue, Seville yellow, etc.).
I adore 1940's kitchenalia, but simply cannot afford it. Not by a mile. Entry-level pieces, such as a common juice reamer, run in the same 25-50 dollar price range that is my absolute top-out for pretty much anything vintage kitchen.
So for now, I find myself concentrating on 1950's kitchen items that are more in my price range. My absolute favorites are the earliest Pyrex pieces and patterns that run from approximately 1945 to 1962, beginning with the Primary colors and running up through the Early American pattern. The early 1960's ushered in gold tones, browns, creams & neutrals that would eventually become the Autumnal color palette of the 1970's.
So I can't afford to to buy thousand dollar canisters and hundred dollar mixing bowls, but I can splurge now and again on a compete Butterprint fridge set - a very reasonable 28 dollars for the whole set with lids! I was shocked to find it that cheaply, in fact. In the very same area, they had the whole set of 4 mixing bowls marked for $100.
Alas, I've definitely seemed to miss the boat on the days when Pyrex was a 50 cent yard sale item. Seeing pictures and posts from people who have gotten fridgies & bowls for 10 cents makes me sigh. I did, however, just buy the very cheapest pieces I've ever gotten from a thrift store just the other day. 1 dollar and 50 cents for the two smallest Shenandoah mixing bowls, in nice condition too, so I can't complain too much. I didn't/don't collect that pattern, but at a buck fifty, I suppose I do now, lol ;-)