I wish I had watched more of the other movies. I spent most of the time confused as to who was who or why they were relevant to each other.
For example, whatever payoff Peter Parker and Tony Stark's relationship had at the end was lost on me since I missed Homecoming.
Unfortunate, but the movie was good enough to enjoy regardless.
I should have seen both Ant Man movies, Spiderman Homecoming, or any of the Gaurdians of the Galaxy movies.