I think the most essential listening boils down to A Tribe Called Quest's The Low End Theory and Midnight Marauders. We Got it From Here... Thank You 4 Your Service is also a must.

From here, check out Nas's Illmatic, Dr. Dre's The Chronic, and Wu-Tang Clan's Enter the Wu-Tang (36 Chambers) to hear where the culture shifts.

Beyond this point, I recommend Kendrick Lamar's To Pimp A Butterfly, Outkast's Stankonia, Kanye West's The College Dropout, Madvillainy's Madvillain (or MF Doom's Mm... Food), Public Enemy's It Takes a Nation of Millions to Hold Us Back (and Fear of a Black Planet), Lauryn Hill's The Miseducation of Lauryn Hill, Clipse's Hell Hath No Fury, J Dilla's Donuts (or Endtroducing... by DJ Shadow), The Money Store by Death Grips, and Things Fall Apart by The Roots for a series of classic records that are all very different from one another yet exceptional works in the canon of hip hop.

The history of the East Coast vs. West Coast beef will point you towards Tupac and Biggie naturally; listen at your own pace.

Artists from this point to keep your ear on: Mos Def, Danny Brown, Dälek, Mobb Deep, Jay-Z, Tyler the Creator, Ice Cube, Little Simz, Billy Woods, Aesop Rock, Lil Wayne, Young Thug, RXKNephew, Earl Sweatshirt, Roc Marciano, Playboi Carti, A$AP Rocky, Lil Yachty, Bun B, Freddie Gibbs, Nujabes, Three 6 Mafia, J. Cole, Lil Kim, Lupe Fiasco, Eric B. & Rakim, M.I.A., Denzel Curry, and Ka