Tonight I wrote a quick program to create 3 word starter sets. It's a brute force approach. Take 3 words from inside the Wordle app at random and extract the letters. Then, starting with the entire list of answer words, remove those extracted letters. The more letters removed, the higher the score. I've noticed that if 9600 or more letters are removed by using the letters from 3 words, that's a pretty good starter set.
So I'm going to let this run overnight and see how many 3 word sets it comes up with that remove more than 9600 letters. It's been running for about 15 minutes and it has come up with only two sets (scores 9602 and 9660), so I think I have the cutoff defined pretty well.