Good question. I actually made my own custom order
- Captain America: The First Avenger (movie is a flashback)
- Iron Man
- Iron Man 2 (picks up right where IM left off)
- The Incredible Hulk (we see Tony performing his consulting role)
- Thor (Post credits scene is a lead-in to Avengers)
- The Avengers
- Thor: The Dark World (First scene with Loki is his trial which would make sense to have happened as soon as possible)
- Guardians of the Galaxy (With Thor back on Earth, the cosmos need a new protector, and the Guardians step into that role; with the chaos in space taken care of we head back to Earth)
- Iron Man 3 (Tony has been having anxiety attacks and has built over 30 suits so we can assume it's been awhile since Avengers, but SHIELD hasn't fallen yet)
- Captain America: The Winter Soldier (mid credits scene leads right in to Age of Ultron)
- The Avengers: Age of Ultron
- Ant-Man (Pym's reference to Sokovia and the post credit scene sandwich it between 2 Avengers movies)
- Captain America: Civil War
- Spider-Man: Homecoming (Takes place 2 months after Civil War)
- Guardians of the Galaxy Vol. 2 (Nebula goes to hunt down Thanos at the end suggesting we don't have too long to wait til IW, however...)
- Doctor Strange (...we know Strange leads in to Ragnarok via the mid credits scene and Ragnarok leads into Infinity War)
*Now, I know Gunn has confirmed GOTG 2 takes place shortly after the first one. But he also said that time in the Guardians' galaxy may work different than time in the Earth galaxy. This also accounts for the Stan Lee Civil War reference in GOTG 2 continuity gaffe. I went with that interpretation rather that just slotting GOTG into Phase 2. So in Guardians time, GOTG and GOTG 2 take place right next to each other. However in Earth time, they are spread out.
Plus I think it just makes sense to put the more fantastical and weird films like GOTG, Strange, and Thor before Infinity War, which has a cosmic baddy.