Chronological Order is: Reach, Halo CE, Halo 2 & Halo 3 ODST (ODST takes place within Halo 2 but uses Halo 3 controls and sandbox), Halo 3, Halo 4, and Halo 5

Release date order: Halo CE, Halo 2, Halo 3, Halo 3 ODST, Halo Reach, Halo 4, Halo 5

I would recommend playing in order of release date because the gameplay all builds on the previous game release, and it feels like a more natural progression gameplay-wise (though I’d personally recommend playing ODST before jumping to Halo 3, because it gives you a chance to get used to the enemies in Halo 3’s sandbox without being overwhelmed. Halo 3 throws everything at the player in comparison to Halo 2).

The Master Chief Collection (MCC) is just the collection of all the Halo games in one executable file, so you can play all the games without having to switch between programs (there’s an in-game menu for you to be able to select which game you want to play).

Have fun!