Not to be religious about it, but any cast iron cookware from China is suspect. They are known to use all kinds of scrap iron and are not to particular about it's previous use (AKA old engine blocks). The Chinese products are typically heavier and bulkier than Lodge and certainly vintage Wagner, Griswold, etc. Some of the Paula Dean have actually been recalled for "exploding" due to air pockets, etc. All of the chef branded stuff is China goods and over priced IMHO.
I cook a lot with cast iron. Not exclusively, but a good deal. I just got done cleaning up my #9 DO and #8 skillet. Made some chilli and some corn bread this evening.
To start get a Dutch Oven. A #9 is optimum IMHO, the #8 can be just a little on the small side for family, #10 just a little bigger than necessary. Any of those three would be fine though. The #8 is best for no knead bred in my experience because of the size and height of the loaf. I've done it in the 9, it was great, but a little lower in height than I like.
Skillets - see if you can get one with a lid or pick up a lid later. #10 would be the size if using just one, add an #8 (skillet cornbread).
I have the big #12 and #14 and like them for cooking things down and for large quantities (browning/searing, etc). They are heavy though. And if you buy lodge or china, they will be a good bit heavier and bulkier than vintage. I like the way everything can go from the cooktop into the oven (although you do this with stainless and copper just fine too).
The DO is great for searing and browning due to the heat retention and the high sides (things don't spatter out).
If you are using big pieces - preheat them in the oven at about 350 or so before putting them on the range. This starts the heating evenly and helps eliminate hot spots.
Getting them seasoned right is key. Maintaining the seasoning is also as well as knowing how to clean them and restore the seasoning is important. Not difficult at all when you understand the process of cleaning, storing, and restoring.
If you are thinking about buying vintage stuff you will be happy with it. That's a whole other deal. You can get very reasonable prices, but often that's because you bought it un-restored, re-seasoned and do that work yourself or buy stuff from the 60's that is less "collectible" but works just great.
Lodge is fine and if you want to just walk into a store and get started that's a good way to go. They have a broad selection of items too which is great.
I have all vintage stuff, gem pans, skillets, DO's, Fryers, waffle irons, oval roasters, bundt pan, cake molds in different sizes. I use it all. You don't need a full set of anything, but it's nice to have a few different sizes.
In skillets I have 3,7,9,10,12,14. The #3 is perfect for two eggs. Seasoned well you can "throw" them to flip. And for browning small amounts. I like to have lids, they can often be more expensive than the skillet and not abs necessary.
I love using them, they are built much lighter have a better finish and season well. Smooth cooking services, etc. Plus it's great conversation when someone walks into the kitchen and sees that you're cooking on something that 100 years old.
As far as vintage goes Wagner pieces are generally cheaper than Griswold. Understand what your buying and you won't over pay.
If you really want to do a quick ramp ask the same question on this website:
Wagner & Griswold Society Forums
Good group of people and you can ask stupid questions. Even if you are going to buy new Lodge. Go to the general info forum and ask away. They will also give you advice before you buy something on Ebay. You don't have to be a member to use the forums in the lower section. The membership gets you into their archives of historical data and deep into the collecting.
Can't recommend it enough even for casual users/buyers of cast iron.
They will also tell you how to restore properly and preserve value.
The thing about vintage cast iron, other than it's overall superiority to whats around today is that it's an antique that you can USE and not worry about it loosing any value. You can strip and re season and bring it all back.
Be careful, it can be addicting
If you buying vintage I can't underline enough to research before you buy anything just yet. You'll be happier and have less regrets about what you may have paid.
I cook with all of my CI, even the waffle irons.
If you buy vintage and know what you are buying you can buy unmarked vintage or non Wagner or Griswold and get them really inexpensive. Wagner and Griswold are higher priced more because you can identify manufacturer, age, and rarity. There's a ton of information out there AFA old catalogs, history that are used to age them. Unmarked is less "collectible" so goes for less money but is equal quality.
I don't think cast iron is the best for everything but I work around the deficits in certain uses pretty well. You just need to know how it "behaves"
I still use my stainless and copper and like them just fine too.