Obviously, I'd start with Cap. He's the foundation stone for the eventual Avengers team, as well as being the first story in chronological order. The film begins and ends in the present, with no mention of the other major heroes in the universe, so it fits nicely at the beginning.

OPTIONAL - MCU EXTENDED:
Watch "Marvel's Agent Carter" Seasons 1-2
directly after this film.

Ironman is next. First time viewers will have been introduced to Tony's father, and Nick Fury already, making IMO a smoother transition into understanding the larger universe.

I've put Ironman II next to give a first time viewer some closure on Stark revealing his identity to the world. I think watching this one before the Hulk gives the Hulk's after credits scene more context.

Hulk is next. It's subtle references to SHILED and Stark Industries should click better with first time viewers now.

Thor is next. Doctor Selvig's comments about Bruce Banner should hopefully click with first time viewers. I think having this one directly before the avengers gives us a nice transition from the earth-based sci-fi of the previous movies, to the outlandish alien invasion motif of the Avengers.

You could put Guardians at the end of Phase Two, but it doesn't matter. Putting it right after Avengers gives us a nice break, and lets Earth rest and time to pass after the invasion, making for a better transition back to the earth based movies. Plus, having been introduced to Thanos in Avengers, seeing him and his servant in this movie directly after will help it click better with first timers IMO.

Vol2. is one of the few Marvel movies that takes place out or chronological order. It happens only a few months after Guardians 1.

The show Agents of Shield helps establish a continuity for us here. The Dark World Tie in episode takes place in the Autumn after Avengers 1. Having this after Guardians will also help first timers in understanding the end credits scene much better IMO.

OPTIONAL - MCU EXTENDED:
Watch "Marvel's Agents of SHIELD" Episodes 8-11 directly after this film.

Christmas after Avengers 1. So it takes place after Thor 2.

OPTIONAL - MCU EXTENDED:
Watch "Marvel's Agents of SHIELD" Episodes 12-16 directly after this film.

Takes place in the spring a year after Avengers 1.

OPTIONAL - MCU EXTENDED:
Watch "Marvel's Agents of SHIELD" Episodes 17-22 directly after this film.

You could place Doctor Strange Elsewhere, but I like him here, as there's nothing really in the movie that connects him to any particular point in time. He was referenced in the previous movie, the Winter Soldier, so hopefully this will help first timers connect those dots a little easier.

OPTIONAL - MCU EXTENDED:
Watch "Marvel's Agents of SHIELD" Season 2, Episodes 1-19 directly after this film.

Phase 2 Complete!

Has to take place after Ultron and before Civil War

I like Thor Ragnarok directly after Ultron, as Thor's dream pool vision, and Hulk's disappearance are two of the biggest unresolved threads, which get resolved in this film. And with no other real ties to other films, I think this is a good place for it. Plus I like how it ties in nicely to Gen Ross' comments in Civil War to have Ragnarok before that film.

OPTIONAL - MCU EXTENDED:
Watch
- Daredevil Season 1
- Jessica Jones Season 1
- "Marvel's Agents of SHIELD" Season 3, episodes 1-19
directly after this film.

Has to be after Antman and before Spiderman.

OPTIONAL - MCU EXTENDED:
Watch
- "Marvel's Agents of SHIELD" Season 3, episodes 20-22
directly after this film.

Has to be directly after Civil War.

OPTIONAL - MCU EXTENDED:
Watch
- "Marvel's Agents of SHIELD" Season 4, episodes 1-8
- Daredevil Season 2
- Luke Cage Season 1
- Iron Fist Season 1
- Defenders Season 1
- "Marvel's Agents of SHIELD" Season 4, episodes 9-22
- Inhumans Season 1
directly after this film.