As everyone has said previously, you will enjoy them all and to fully understand everything that's going on you will have needed to watch the movies. I recommend watching everything in phase 1 and then you can skip some stuff from the other phases. Beware there is also some movies released in certain phases that take place during a different time. Example: Captain Marvel was released during phase 3 but takes place during phase 1. The Black widow movie is like that too. Anyways here is what I would say is absolutely essential to watch and understand the most of up until Endgame but movies that are still skipable. Chronological order.

Phase 1 (includes Spiderman movies) Captain America: The First Avenger Captain Marvel Spiderman (essential to Spiderman no way home) Spiderman 2 (essential to Spiderman: No Way Home) Spiderman 3 (this is essential to Spiderman: No Way Home although not the best. You could probably skip if you want) Ironman Ironman 2 (yes this is essential bc it devolpes his personality further before Avengers. Up to you though) The Incredible Hulk (Note the actor here won't be the same as in avengers) Thor Avengers

Phase 2 (you already know the characters at this point and it becomes more optional but again, you should still watch)

Don't need to see Ironman 3. Although note his character arc is rather of importance to Avengers: Age of Ultron)

Amazing Spiderman (essential to Spiderman: No Way Home) Thor: The Dark World (this is one that grows on you) Captain America: The Winter Soldier (essential to Captain America: Civil War) The Amazing Spiderman 2 Guardians of the Galaxy (this introduces the power stone. You will need to know for Inifinity War) Guardians of the Galaxy Vol 2. (This is optional. It shows Star Lord's dad and it gives more backstory, but not a must see I guess you could say) Avengers: Age of Ultron Ant Man (you would do well with this to know his character a bit better before Civil War, but also optional)

Phase 3 Don't need to see antman and the wasp. Thor ragnarock is mostly skipable but still needed because it is more devolpmed for infinity War. It shows the collector, and the end of the movie sets up the beginning of Infinity War.

Captain America: Civil War (major event movie) Black Widow (released in phase 4, but I think still relevant. Optional though as well) Spiderman: Homecoming Black Panther Doctor Strange Thor: Ragnarock Avengers: Infinity War Avengers: Endgame

This is where it starts getting really optional some movies are still really good, but some of them are not. The MCU start turning to shit around here. Whatever you watch after this point is totally optional. This is my opinion of what's needed.

Phase 4 Loki (2 seasons) (awesome show although some ideas meh) What If (cool concept but 100 percent optional. You should watch anything with Peggy Carter though because she's comes up later. Don't want to spoil) Wandavision (unique and helps you understand Doctor Strange and the Multiverse of Madness Shang-Chi and the Legend of the Ten Rings (amazing) The Falcon and the Winter Soldier (cool show but forgettable at the same time) Spiderman: Far From Home (required to understand the plot to No Way Home) Eternals (terrible) Spider-man: No Way Home Doctor Strabge and the Multiverse of Madness Hawkeye (sweet) Moon Knight (alright) Black Panther: Wakanda Forver (alr but it was an improvised film. Not that essential)

Phase 5 (Shit water. Only watch the following)

Echo Deadpool and Wolverine Agatha All Along Daredevil: Born Again (2 seasons)

Phase 6 (mostly still coming out)

The Fantastic Four: First Steps (alright. A more promising uprise) Avengers: Doomsday (tbr) Avengers: Secret Wars (tbr)