There's a lot of items here - so what do you really need? I'd say to start with the 10 inch chef pan, the item I use most, and expand from there as the need arises. Of course if you're cooking for a bunch of people all the time you might want instead to consider the 12 inch model instead. If you are interested in ethnic cuisines I'd also take a look at the Round Griddle, a very useful item.
There are two types of iron pans - cast iron and sheet steel. Cast iron pans are relatively thick and heavy with good heat retention. Sheet steel pans are thinner and much more responsive to changes in heat. Both have their uses and both are seasoned and maintained about the same. Steel, by the way, is just very pure, low carbon iron with carefully controlled contaminants.
Many of the items mentioned here are by Lodge Cast Iron. There are other manufacturers for at least some of these items, but Lodge is the most easily available, of excellent quality and not made in China (their enameled iron line is made in China though).Cast Iron Pans
Cast Iron Deep Skillet w/Cover
Cast Iron Chef's Skillet
I also have a 9 inch cast iron chef's skillet from an unknown US
manufacturer that's absolutely perfect for making a 4 egg tortilla (an inch
thick Spanish omelet). The gently rounded sides make it easy to turn the
omelet out and slide it back in on the other side, and the heavy iron is
non-stick and distributes the heat perfectly. It's also very nice for
smaller frying jobs.
Cast Iron Skillet
Cast Iron Round Griddle / Comal / Tava
Cast Iron Bastable Oven
Cast Iron Wok
I have found the cast iron wok less than ideal because it takes a long
time to heat up and doesn't respond quickly to changes in heat from the
burner. My aluminum core stainless wok is much faster, but for true Chinese
level temperature control you want a sheet steel wok (see below).
In Mexico the comal is more often of cast iron, or out in the villages of
pottery, but this US made 11 inch sheet steel version also serves very well
for heating Tortillas, Chapatis, Roti, Pappadam and other flat breads. Since
I also have the Lodge Round Griddle / Comal listed above, I use this comal
mainly as a surface upon which to blast bell peppers and chilis with a butane
torch - the only practical way to peel peppers.
Sheet Steel Omelet Pan
This 9-1/2 inch pan is perfect for 3 egg omelets. I presume it would do
4 egg omelets just fine too, but I always make them with 3 eggs. An omelet
pan should never be washed. Should some egg stick to it (and it should not),
you scrub it out with coarse salt and a paper towel. It is used only for
French omelets, cooked in butter - nothing else.
Sheet Steel Wok
This most excellent wok was made in the late 1960s by Atlas Metal
Spinning in San Francisco - but it is my impression they are no longer
in business. It is 14 inches in diameter - about the largest practical
on a kitchen stove, while 13 inches is the bare minimum for a wok.
Sheet Steel Indian Kadhai
The photo specimen, which I use for all my deep frying, is 14-1/2 inches
diameter, made of heavy sheet steel formed in a press (thus some rippling
around the edges). It was purchased from an Indian appliance store in
Los Angeles, but that store no longer sells any "authentic" Indian stuff,
just cheap junk. Fortunately, I have found India Sweets and Spices in
Glendale CA now has real kadhais in several sizes (early 2017)
Details and Notes.
Enameled Iron is superb for braising, but for stovetop frying it has some of the same problem as stainless steel. It soon becomes not so good looking because of oil turning to brown varnish on it, which is why black enamel is used for most enameled skillets. Also, it doesn't take seasoning as well as bare iron so could have sticking problems.
Enameled iron is very sensitive to heat shock from sudden temperature changes and you need to be careful of that - don't pour cold stuff into a hot pan or the enamel may spall, and let an over-heated pan cool slowly almost to room temperature before attempting to clean it. People report spalling during rapid stovetop heating as well, particularly when new (probably invisible manufacturing defects). Make sure you get a good warranty and keep the paperwork.
Enameled iron is not eternal, because the enamel on the inside eventually dissolves. I had to retire a Le Creuset saucepan and a really nice Copco sauce pan due to bare iron being exposed after about a decade of very frequent use. The taste of iron in your soup is to be avoided.
Another consideration is that stovetop vessels are moved around and manipulated a lot, and enameled iron is even heavier than regular iron, and more fragile.
The big name in enameled iron is Le Creuset. Their quality and durability are excellent but their pricing is absurd - at least twice what it reasonably should be (a 5-1/2 quart Dutch oven is US $310 list, $230 on Amazon).
Caution: Most low cost enameled cast iron cookware is made in China, land of lead, melamine and every possible form of cheating on quality. You need to purchase from a major US brand that backs the quality and provides a warranty. About 10 years ago I bought an oval Dutch oven of Chinese brand, and iron was showing through the enamel after only a few uses.
Lodge has a line of enameled cast iron cookware from China that's getting good reviews (4-1/2 stars out of 5 on Amazon). Some report early failure of the inside enamel but that should be covered under warranty. Once it's been used for awhile it should be fine unless abused.
Shown in the photo are my three enameled iron dutch ovens, all purchased
in the late 1970s, and used almost entirely on the stovetop. The 3-1/2 quart
oval (Le Creuset) has been far and away the most used. The 5 quart
(Descoware, Belgium - no longer made) has seen substantial service and the
7-1/2 quart (Copco, Denmark - no longer made), wonderfully light for its size,
has been used mostly at parties to warm and serve stews and other dishes
cooked in stainless steel pots. The Le Creuset needed the knob replaced
(with a ceramic drawer pull) and shows some bare iron but I still use it
now and then for non-acidic foods. I'm too cheap to buy a new one at
their current prices.
This form of cookware was very popular a few decades ago before multi-ply stainless came on the scene, and is still sold but to a much lesser extent. Graniteware roasting pans are probably the most widely used. It's main advantages were low cost and light weight compared to enameled cast iron and better heat distribution than with single ply stainless. Being enameled it has the same bright colors, inertness and corrosion resistance as enameled iron.
The main disadvantage of this construction, and a major reason it has fallen out of style is that it is easy to chip, so must be handled gently. a sharp hit on an outside corner will bend the steel enough to cause a spot of enamel to spall off on the inside. From this point on that spot rusts. This is not a serious problem for cooking most foods, but that spot will eventually rust right through.
The photo shows a steamer pot made in Holland. It was obviously designed by morons because the lid fits the steamer top but is too small for the pot. This means it can be used only as a steamer and not do double duity as a regular pot. Really dumb.Seasoning and Maintenance
Cast iron (non enameled) and sheet steel cookware needs to be seasoned before it's used, but seasoning is not the hassle some people make it out to be. Seasoning is basically a coating of oil that has filled the pores in the metal, coated the surface completely and dried to a sort of varnish. A good seasoning is very non-stick, and unlike teflon non-stick coatings is self healing if scratched.
Seasoning doesn't have to be thick, black or opaque, it's fine to be able to see the metal through it. It's also fine for it to be opaque, but you shouldn't let it get too thick or it'll start flaking off in your food.
Maintenance of cast iron and sheet steel cookware is easy.