I want to watch all the DC animated movies and series from the beginning. Which order should I watch them?

There isn’t much continuity in the ones that fit together, so you dont have to watch them in order to “understand more” or anything like that. Annyway: wikipedia got you coverd for the rest:

Stand-alone films[edit]

The following films are stand-alone, and do not share continuity with each other or other films:

• Superman: Doomsday
• Justice League: The New Frontier
• Wonder Woman
• Green Lantern: First Flight
• Batman: Under the Red Hood
• All-Star Superman
• Green Lantern: Emerald Knights
• Superman vs. The Elite
• Superman: Unbound
• Batman: The Killing Joke
• Batman: Gotham by Gaslight

Superman/Batman[edit]

This continuity is based on the Superman/Batman storyline.

[150]

• Superman/Batman: Public Enemies
• Superman/Batman: Apocalypse

Justice League (JLA)[edit]

This continuity is based on the JLA storylines published in 2000.

[151]

[152]

• Justice League: Crisis on Two Earths
• Justice League: Doom

The Dark Knight Returns[edit]

Main article: Batman (The Dark Knight Returns)

This continuity is based on Frank Miller's The Dark Knight Returns.

[153]

• Batman: Year One
• DC Showcase: Catwoman
• Batman: The Dark Knight Returns Pt. 1
• Batman: The Dark Knight Returns Pt. 2

DC Animated Movie Universe[edit]

This shared universe is mostly based on The New 52 continuity.

[154]

• Justice League: The Flashpoint Paradox (only the end)[155]
• Justice League: War
• Son of Batman
• Justice League: Throne of Atlantis
• Batman vs. Robin
• Batman: Bad Blood
• Justice League vs. Teen Titans
• Justice League Dark
• Teen Titans: The Judas Contract
• Suicide Squad: Hell to Pay (upcoming)
• Death of Superman (upcoming)
• Reign of the Supermen (upcoming)

Justice League: Gods and Monsters[edit]

This takes place in a universe where different characters have the roles of Superman, Wonder Woman and Batman, and as such they are portrayed as darker characters.

[156]

• Justice League: Gods and Monsters
• Justice League: Gods and Monsters Chronicles (web series, serves as a companion piece)

Other universes[edit]

• Batman: Gotham Knight (set in the Nolanverse)[157]
• Batman: Assault on Arkham (set in the Arkhamverse)[158]
• Batman and Harley Quinn (set in the DC animated universe)[159]