First, play WC1 and WC2, and the WC2 expansion, "Beyond the Dark Portal". The Orcish campaign of WC1 is the canon ending, and the human campaigns of WC2 and BotDP are the canon ending. You should also read the manuals as a lot of important lore is tucked away in them but isn't outright explained in the game (remember, these games are from the 1990s, when people were still expected to read manuals and important stuff was put in them).
Before you jump into WC3, you should read a few books.
Rise of the Horde goes back to the WC1 era and shows the formation of the Horde on Draenor. This novel is important in establishing what Orcish society looked like, showing how Draenor was destroyed, establishes the key Orcish characters, and sets up Grom's character arc for WC3.
Of Blood and Honor establishes what Paladins are and introduces the character Tirion Fordring, who will become important later on.
Lastly, youu should read Lord of the Clans. After WC2 was released, a guy called Chris Metzen stepped up and became the head writer in charge of the Warcraft storyline. He pushed for an adventure game called "Lord of the Clans" to be made that would setup Warcraft 3, but the game was cancelled, and the events of the game published as a novel. Warcraft 3 directly continues where Lord of the Clans ends.
There are other novels set during this time period, but those are the really important ones. Also, most Warcraft novels are... well they're just not very good. I'm a Warcraft lore nut, and even I wouldn't really recommend that you waste your time reading them. If you want to read good fantasy fiction, go read Dragonlance or The Black Company or something.
Okay, now you play Warcraft 3. Read the manual first, though. Play the campaigns in order. Then the expansion, The Frozen Throne. Then you play the Bonus campaign.
Read the WoW comic, namely the first arc: the Onyxia storyline. This establishes the character of Varian Wrynn, the King of Stormwind. Don't bother reading past the Onyxia arc as the comic goes bad.
Next, you play World of Warcraft, namely the Vanilla storylines located on Kalimdor and the Eastern Kingdoms. You're going to need to create two characters: one on the Alliance side to do their storylines, and one on the Horde side. There isn't really a main storyline at this time, but there are a few important storyliens:
-On the Alliance side, you should do the Westfall questline (which climaxes with the Deadmines dungeon). Then do the Blackrock Mountain storyline (begins in Burning Steppes and climaxes with the Molten Core raid).
- On the Horde side, you should do the Barrens and Ashenvale questlines to get a feel for the struggles the Horde faces, and the tensions with the Alliance.
That's the main gist of Vanilla WoW. Then you move on to the Burning Crusade expansion. Now, be warned that the writing for TBC was wonky. There are quite a few retcons of prior lore, and WC3 characters being uncharacteristically shoehorned into evil. Here are the important questlines you should do:
- You should create a Draenei and a Blood Elf character and do their starting questlines to get a feel for what they are about.
- Do the Escape from Perneholde dungeon. This let's you play through the Lord of the Clans story, and it also sets up the Ashbringer storyline that will take center stage soon.
- On your Horde character, go to Nagrand and do the Mag'har storyline. This is one of the best Horde storylines in Warcraft, and introduces the character of Garrosh, who will be very important later on.
- Do the Sunwell storyline: unlock the Isle of Quel'danas, then do the Magister's Terrace dungeon, then finish off by doing the Sunwell Plateau raid.
Then read the Ashbringer comic.
Next is the Wrath of the Lich King expansion.
- Create a Death Knight character and do the starting questline. It's bloody fantastic and sets up the rest of the expansion.
- Do the Dragonblight questline. Sadly, parts of this questline have been removed from retail (particularly the climatic Battle for the Undercity event).
- Do the Storm Peaks questline, then do the dungeons in the area, then watch the 3.1 trailer, then do the Ulduar raid. This reintroduces a WC3 character, and introduces the Titans and their lore, which will be important going forward.
- Do the Icecrown citadel questline. ESPECIALLY do the Crusader Bridenbrad questline in Icecrown.
- Do the Trial of the Crusader, then watch the 3.3 trailer, then do the Icecrown Citadel raids.
I should warn you that there is another big storyline happening at this time, mainly the stuff with the Dragons. I have left this story out because it is not core to the Warcraft story, and I don't think it is very satisfying.
Then read the short story, Heart of War.
Next, you should read the Shattering novel. This book sets the stage for the Horde vs Alliance war arc and develops their characters.
Next, you play Cataclysm.
- Create Worgen character and do their intro storyline, which depicts the Alliance perspective of the invasion of Gilneas. It is very good.
- After you have done the Worgen storyline, create a Forsaken character and go through their starting storyline, and then do the Silverpine Forest questline. This shows you the Horde perspective of the invasion of Gilneas.
- On a Horde character, you should do the Stonetalon Mountains questline.
- Do the Vash'jr and the Twilight Highlands questlines, which depict the Horde vs Alliance war.
- Do the Dragon Soul raid.
Next, you should read Tides of War, which is about Jaina and escalates the war. Once you have finished Tides of War, hop back into WoW and play through the Theramore's Fall scenario, which depicts those events ingame. Also do the Blood in the Snow scenario.
Then you play Mists of Pandaria.
- Create a new Pandaren character and do their intro questline. It's very good.
- Do the Pandaria questing experience. You will want to do the Jade Forest intro twice as Horde and Alliance characters have different intros. The zone questing order is: Jade Forest > Valley of the Four Winds > Kun-Lai Summit > Townlong Steppes > Dread Wastes.
- Do the MoP legendary questline. This has been removed from retail WoW.
As you are doing the MoP legendary questline, you will also want to do other questlines as they come up:
- Do the Mogu'shan Vaults raid, then do Heart of Fear (after you've finished the Dread Wastes questline). Then do the Terrace of the Endless Spring raid.
- Do the Shieldwall and the Dominance Offensive questlines (you will need to do them on your Horde and Alliance characters to get both perspectives).
- Do the Isle of Thunder questline (doesn't matter which side you do it on), and then do the Throne of Thunder Raid.
- Do the Dark Heart of Pandaria scenario.
- Do the Battlefield Barrens questline. This has been removed from retail WoW.
- Watch the "Burdens of Shaohao" cartoon on Youtube.
- Watch the 5.4 trailer.
- Finish the MoP legendary questline and do Siege of Orgrimmar.
Then you read the book: War Crimes. I haven't read it again but from what I recall it was pretty okay, but the Garrosh and Anduin scenes were pretty good. Also, the premise for the next expansion makes no sense unless you've read this book.
Then read Warcraft Chronicle. This is a lore book and mostly rehashes lore you already know (and retcons a ton of stuff), but it is important for introducing the Light vs Void conflict, explains the old gods, gives us a breakdown of the history of Azeroth prior to the War of the Ancients, shows us the Titans, and explains the Burning Legion.
Watch the "Lords of War" cartoon on Youtube.
Then play Warlords of Draenor.
- Do the whole questing experience.
- Do the legendary questline (again, removed from retail).
- Skip the Highmaul raid and just do Blackrock Foundry.
- Watch the 6.1 and 6.2 trailers.
- Do the Hellfire Citadel raid.
Then read the 2016 Illidan novel. This retcons Illidan from his wonky TBC depiction and sets the stage for the Legion expansion. Also, watch the Harbingers cartoons.
Then play Legion.
- Create a Demon Hunter character and do their intro questline.
- Do the Broken Shore intro.
- Do the Val'sharah and Stormheim questlines.
- Do the Death Knight class order hall questline. This sets up Shadowlands.
- Do the Illidan questline.
- Do the Emerald Nightmare and the Nighthold raids.
- Do the Broken Shore zone questline, then do the Tomb of Sargeras raid.
- Do the Argus questline, then do the Antorus raid.
Read the Before the Storm novel.
Then play Battle for Azeroth.
- Do the BFA intro, which is the War of Thorns prepatch storyline. It's extremely good. Then do the Battle for Lordaeron scenario. Also very good.
- Read the short stories "A Good War" and "Elegy".
- Do the BFA questing experience. You will need a Horde and an Alliance character to do both stories.
- Do the War Campaign. Again, you need two characters.
- Do the Battle for Dazar'alor raid.
- Do the Nazjatar questline, then do the Eternal Palace raid.
- Do the Ny'alotha raid.
Then you read Shadows Rising.
Watch the Afterlives cartoons on Youtube.
Play Shadowlands.
- Do the questlines in order. Note that several quests have been removed from retail.
- If you really want to do a Covenant Campaign for the story, then do the Ardenweald one. It's the only covenant that actually gets stuff done.
- Do the Castle Nathrai raid.
- Do the Korthia questline and then do the Sanctum of Domination raid.
You are all caught up on the Warcraft storyline.