Building a 100 album vinyl collection 3 must have albums are?

There is a lot of good suggestions , some of which I would agree with so I'll give you 3 different ones from 3 different genres  ( plus 1 ) .

Jimi Hendrix  "Electric LadyLand " 

Joni Mitchell   " Ladies of the Canyon "

Solti & CSO  Beethoven's 6th symphony " Pastoral "

plus 1

Julie London  " At Home "

If you can stretch the budget, MFSL One-Step Ultradisc are about as good vinyl records get IMHO:

1. Muddy Waters - Folk Singer

2. Eric Clapton - Unplugged

3. Crosby Stills and Nash

This is what Michael Fremer said about the Santana Abraxas MFSL Ultradisc:

"Halfway through this "one step"’s side one I said to myself "This might be the best record I’ve ever heard". I meant by that the technical quality of the record and how much it resembles tape in four critical parameters: the wide dynamics and low bass response, the unlimited dynamic range, the tape-like sense of flow and especially the enormity of the soundstage presentation. More importantly I got a greater appreciation for the music, the musicianship and the showmanship too."

High praise indeed! You can read the full review here:

https://www.analogplanet.com/content/mobile-fidelitys-one-step-abraxas-any-record-worth-100-0

Roy Harper - Flashes From the Archives of Oblivion 

Leonard Cohen - Live in London

Tom Waits And Crystal Gayle – One From The Heart

Peo Alfonsi Alma

Peo Alfonsi Amada

Josep Colom Musica Callada

DSD 128

@stereo5 

"Why would you need suggestions from others as you may not like what I or other people like? "

So you can discover new ideas and expand your pallet.