Hello Baden,
Why don't opt for a Buren, Lemania and Eterna WWW first so that you can complete more of the dirty dozen. My advice is to look for Omega WWW ASAP as it is still in fairy cheaper price range, then go for JLC WWW, Longines WWW and IWC WWW. The main issue about completing the dirty dozen is Grana WWW which is super rare and needs a lot of patients and lucks to find one for sale. Even one pop up for sale, definitely has a big price tag and a lot of buyers that are willing to pay one to complete the set. There is Grana WWW for sales in the bay recently for around USD3800.
Below is my dirty dozen picture for your reference
Regards