Ok, so I’m gonna consider only story arcs at first.
The Fifth Doctor, Nyssa, Tegan and Marc
Tartarus
Warzone/Conversion
Time Apart
Thin Time/Madquake
The Lost Resort
The Perils of Nelly Bly
Nightmare of the Daleks
Included 5DAs because the story arc concludes there. I only left out one release (Interstitial/The Feast of Fear). Not essential and not breathtaking, but you can add it if you want as there is not any room to breathe between Marc’s introduction and a key plot point that happens in Warzone.
The Fifth Doctor, Tegan, Turlough and Nyssa
Circular Time
Cobwebs
The Cradle of the Snake
The Emerald Tiger
The Jupiter Conjunction
The Butcher of Brisbane
The Lady of Mercia
Prisoners of Fate
Mistfall
Equillibrium
The Entropy Plague
Only Cobwebs, Cradle, Prisoners, Mistfall and Entropy are truly essential here. Mistfall is not good at all but a bit important. You could argue I left out two important stories for Turlough (Kiss of Death and Eldrad Must Die!) but they are not worth it. Jupiter and Butcher are fine/good, worth a listen, but Tiger, Mercia and Equillibriun are fantastic non-essential audios.
Circular Time is solo Nyssa but very, VERY important for this arc.
The Fifth Doctor, Peri and Erimem
The Eye of the Scorpion
The Church and the Crown
The Council of Nicaea
The Kingmaker
Son of the Dragon
Mind’s Eye/Mission of the Vyrians
The Bride of Peladon
Erimem is a interesting character because modt of her worthy stories are historicals. I would argue maybe The Axis of Insanity and The Roof of the World are worth it from the ones I left out. Axis is fine; the first hour of Roof is great then it loses a lot of momentum.
The Sixth Doctor and Evelyn:
The Marian Conspiracy
Project: Twilight
Jubilee
Doctor Who and the Pirates
Project: Lazarus
Arrangements for War
Thicker Than Water
You can argue Jubilee and Doctor Who and the Pirates are not essential. I absolutely disagree and argue back that they are key to Evelyn emotional development that leads to the end of Lazarus. Bloodtide and Real Time are non-essential but great; and The Apocalypse Element is a nice addition to Neverland-Zagreus and essential to the Gallifrey spin-off.
The Sixth Doctor and Jamie
City of Spires
The Wreck of the Titan
Night’s Black Agent
Legend of the Cybermen
Only one not essential is Night’s Black Agent which is a companion chronicle, but it’s good so give it a shot. Legend of the Cybermen is my favorite Cybermen story ever and perhaps ij my top 5 Who ever, soooooo…
The Sixth Doctor, Flip and Constance:
The Crimes of Thomas Brewster
The Curse of Davros
The Fourth Wall
Wirnn Dawn
Scavenger
Criss-Cross
Shield of the Jotunn
Absolute Power
Quicksilver
The Behemoth
The Middle
Static
Scorched Earth
The Lovecraft Invasion
Ok, Flip and Constance don’t actually have a story arc hapenning but I want to promote them. The Crimes of Thomas Brewster is actually a Evelyn story but it’s great and Flip’s first appearance. Besides featuring another recurring Sixth Doctor character. The Fourth Wall, Wirnn Dawn and Shield of the Jotunn are not really essential to this era, but they are all great and if I didn’t put them you would have a really awkward sequence of stories where you don’t fell the companion travelled with the Doctor at all.
Any story featuring Constance in the World War is key to her character, so it’s a must for Criss-Cross, Quicksilver and Scorched Earth. I would argue the short trip Darkened Earth should be listened too. Static do A LOT for these two and The Middle is just too fun to leave out. I included The Lovecraft Invasion because it introduces a recurring character for the era.
The Seventh Doctor and Ace
The Fearmonger
Colditz
1963: The Assassination Games
None of these are essential but they are all good stories and give a nice entry point for post-Classic Seven and Ace without dipping in the Hex era yet. Colditz is important later for Klein, and 1963 is a really coold backdoor pilot for the Counter-Measures. You can listen to The Genocide Machine and Dust Breeding as it introduces a character relevant later in Benny’s life, but they are not as good.
The Seventh Doctor, Ace and Hex - against the The Forge
The Harvest
LIVE 34
The Settling
Forty-Five
The Magic Mousetrap
Enemy of the Daleks
The Angel of Scutari
Project: Destiny
A Death in the Family
The Seventh Doctor, Ace and Hex - the Elder Gods
Protect and Survive
Robophobia
House of Blue Fire
Black and White
Gods and Monsters
Project: Nirvana
Afterlife
Signs and Wonders
The Harvest introduces Hex, LIVE 34 is too good to leave out, The Settling, Enemy of the Daleks and The Angel of Scutari are all really important stories for the dynamic of the team, Forty-Five introduces some key ideas for the era and I would argue The Magic Mousetrap is when the Elder Gods arc starts. Project: Destiny and A Death in the Family is an epic finale for the first half.
All of the cited stories in the second half are important except for Robophobia. I would listen anyway because it introduces a character important later in the Doctor’s life, is a good story and adds up to the fell that the Seventh Doctor has been doing some stuff… Please skip Revenge of the Swarm and Mask of Tragedy. Not worth it.
Oh, Muse of Fire is a later release that happens early in Hex travels that I like a lot. A good extra audio if you want some.
The Seventh Doctor and Klein
Colditz
A Thousand Tiny Wings
Klein’s Story/Survival of the Fittest
The Architects of History
UNIT: Dominion
Persuasion
Starlight Robbery
Daleks Among Us.
Yup. All important. The second Klein triology os not well-liked and many would say not worthy it, but I really like it and say: worth a shot!
The Eighth Doctor and Charley - The Web of Time
Storm Warning
The Stones of Venice
Solitaire
The Chimes of Midnight
Seasons of Fear
Embrace the Darkness
Neverland
Zagreus
Ok, there are only four essential audios here: Storm Warning, The Chimes of Midnight, Neverland and Zagreus. But for me that feeling that the Doctor and the companion have been travelling between key moments for their characters is really important, which is why I add non-essential but good stories like Seasons of Fear and Embrace the Darkness. Solitarie is a companion chronicles but it’s fantastic so here it is.
The Eighth Doctor, Charley and C’rizz - the Divergent Universe
Scherzo
The Creed of the Kromon
The Natural History of Fear
The Last
Caedroia
The Next Life
All truly essential except for The Natural History of Fear. Which for me is a fantastic story. I know some people in the forum disagree quite strongly, but I say it’s worth it. Plus adds atmosphere to the feeling of this era. I wish I could spare everyone from The Creed of Kromon, but I can’t.
The Eighth Doctor, Charley and C’rizz - I don’t have a good name for this one
Terror Firma
Other Lives
Time Works
Memory Lane
Absolution
The Girl Who Never Was
Time Works is not essential but I find it a great underrated gem. Memory Lane is not essential but it’s well-liked. The rest are important. I left out Something Inside, an audio I have lots of fun with but with a very debatable quality.
The Sixth Doctor and Charley
The Condemned
The Doomwood Curse
Brotherhood of the Daleks
Patient Zero
Paper Cuts
Blue Forgotten Planet.
All essential except maybe for The Doomwood Curse. I would still listen to it. It comes with the footnote that a word that is considered a slur for Roma people is said a lot, which takes away from my enjoyment from a otherwise fantastic story.
It’s a complex subject and to be fair I come with a non-UK perspective as in UK I think the word is prefered by some Roma groups? but I thought I should put a warning in anyway because it bothered me first time I listened.