If we click on the Conservatives for Women Facebook page, it will become part of Facebook tracking of us – probably even if we don't have a Facebook account.
I can't remember the current state of play on this, but AFAIK Facebook creates "shadow identities" (what Line of Duty would call nominals) where it tracks people across the web via cookies on every site which has the Facebook link – so, most sites inc MN – even if Facebook doesn't know the person's actual name. Device Identification is also carried out by many websites: you'll often see it mentioned in the same warning as cookies. Can't remember details just now, but basically IIRC our actual smartphone or home router's short-lived link from the exchange is identified. (Don't shoot me if that bit's wrong, I'm tired and can't remember stuff today. I'm sure someone can do a better rundown of all aspects of tracking)
I've just looked, and the Conservatives for Women website states: "We use cookies to ensure that we give you the best experience on our website" and does not appear to give any way to opt out of cookies as many other websites do. It would be better practice for them to allow us the choice to opt out.
Donations and sales of postcards are via PayPal. The site says that the service may collect data about the buyer. I don't know how much data this sort of vendor can get about PayPal buyers, although I think I get email addresses when I sell stuff and do money transfers.
Typically the value of this data comes from aggregating and cross-referencing data sets. So the same buyer of flowers also buys a Ravelry magazine, has used their email address to join a website about motor-racing and on the same device has watched a YouTube clip about chasing Donald Trump round his golf course with a tuba. This allows anyone doing marketing to have a fuller picture and thus isolate a target audience, which they can microtarget with a message not necessarily meant for general consumption.
Facebook sells marketers "universes" of accounts they've identified as likely to respond to the same sort of issues or style of marketing. So once we're in a universe from one site we've visited, we may be nudged towards another.
Eg one of the Leave campaigns harvested data from disengaged potential voters via a football prize competition. It then used this data to bombard people with specially tailored political ads. Vote Leave didn't need to know people's actual names, just how to reach them and what would press their buttons.
Vote Leave's targeted Brexit ads released by Facebook
www.bbc.co.uk/news/uk-politics-44966969
en.wikipedia.org/wiki/Dark_advertising
I only mention Vote Leave and Facebook because it's a well-studied example: anyone who wants to pay for it can do this and can use various platforms. During the run-up to the 2016 US election, I kept finding Breitbart cookies on my machine. I hadn't been on the Breitbart website and the most likely culprit was actually adverts or some other content on MN, although I had an ad blocker at the time.
So yes, it's excellent practice to use throwaway email addresses, but that's not enough to prevent us being tracked and fed tailored content.
Sorry, that was a long diversion on non-obvious data collection and uses.
It does not follow that WfC are going to use our data (mine too, because I clicked) like this! But like everyone else they could if they wanted to.