I went in the order when Key had started with Kanon, then AIR, CLANNAD, Little Busters!, then skipped to Rewrite afterwards. I was hesitant about playing Tomoyo After, especially with the H-scenes because it was hard for me to view that type of stuff but I played other games that were similar to it (though I should feel ashamed reading them in the first place). I never even played Kud Wafter before because I was hoping they would have an official release, being of course the all-ages version instead of the 18+ version but I guess not.
Other than that, I decided to also play Planetarian because I heard how interesting the story and I gave it a try and I plan on buying the HD release soon. It is actually easier for me to buy them from Steam since I made an account some time ago and it would help those who put so much time and effort into creating them could continue to inspire us as readers who love and enjoy these works.
EDIT (9/8/16) I’ve read Planetarian several months ago which was really inspiring and enjoyable to read. I’m finishing up with Tomoyo After for the Steam release and I can say that I appreciate the re-read a lot more than I bargained for since I played the 18+ version a few months ago. I’m almost finished with Little Busters! EX because I was curious to read the EX routes that I heard were good, especially Saya’s route. I plan on reading Kud Wafter anyways which I’m going to play as well despite what others may say about the game.