I don't know if this actually makes things better or worse - I do it in the hope I can shut down spam by removing a compromised address - but I try very hard to use a different email address for every business I purchase from.

You don't always have to provide a phone number, either. Most of the time yes, but I don't think the phone number is actually required to complete a credit card transaction.

There also used to be credit providers - maybe there still are? - that would let you generate a new card number for each purchase. That too may accomplish nothing from a tracking perspective, since the credit provider would be able to match up all the numbers. But, if I had that capability, I would use it.

Obviously you can't but the point people don't realize is that if you use that same card in store the merchant can link it back to online purchases you made and all your information which they can then package and sell to data brokers.

There are credit card services that provide some privacy, such as proxies: I've heard of Abine, Privacy, and something called Final, but I haven't looked into them.

I try to use Offset credit when possible - yet only with nerd friends

you can't