I used to recommend Anolon, but unfortunately they discontinued their enameled cast iron. I much prefer the slightly rough, black enamel style of Staub. I find it sears much better, at the cost of being a bit tricky to keep clean.

You can often find sales on individual Le Creuset and Staub pans on Amazon, bringing them down to around $100. I do have my eye on a Le Creuset skillet that has a black enamel.

All-Clad often has individual D3 pans on sale on their site, and they regularly have factory seconds and packaging damage on sale at https://homeandcooksales.com/. You can subscribe and get notified when they have an event, they don't go overboard with emails.

Don't feel like you need to buy everything at once, or even stick to one brand. You might get a 9" skillet here from All-Clad, see a Fissler Original-Profi sauce pot on sale there. Then decide you want to splurge on a saucier, because a saucier is worth splurging on, from Falk when they have a 15% sale. There's something to be said for having the bulk of your collection from a single brand for the sake of lid interoperability, but there's also something to be said for sniping the best in class for each piece when you find a deal.

Just don't buy sets, it's a sure way to get stuck with pans you don't really use.