I wrote a detailed post that got hung up here and vanished. @simonmoon is correct in asking if you are looking for sonic spectaculars or good music. Sometimes, they overlap. The better remasters often sell out and are costly; the OGs are often misgraded and overpriced. I could give you a list, but without knowing your musical taste it would be kind of pointless. I used to have a couple shelves of "demo" records but got to a point where I abandoned that- at peak, I had around 17k LPs, but winnowed it down to around 5k records when I moved from NY to Texas and probably acquired another 1k since then. The London Jazz Collector is a good resource for older jazz. I write a blog- not promoting it here- I don’t take ads and it costs me several thousand a year to maintain it.
Give us more info on what you are chasing. I’ve slowed down in purchases because of price and grade inflation. A lot of newer reissues are pulled from a digital source which is one reason why analog buffs try to source OGs. Among them I would include the UK first on EMI/Columbia blue/black label of Jeff Beck’s Truth -it sounds like no other copy I have been through a dozen or more; ditto Alice Cooper’s Love it To Death cut by Randy Kling on Straight (Zappa’s imprint). Hard to find a clean copy partly b/c it is collectible for the cover art. Oliver Nelson’s Blues and the Abstract Truth recut by Chad at 45 is a straight ahead jazz record (not too "out there") but you could pay 175 US plus shipping for a clean copy. Alice Coltrane’s Ptah, the El Daoud is great as an OG. It was not reissued for decades-- the current reissue is pulled from a digital file which I have not heard. The OG is pricey.
So, give us more insight into what you are after and I’m sure you’ll get more meaningful responses. I collected UK Island Pink Labels, UK Vertigo Swirls and among other smaller and now costly label issues, Strata East and Nimbus West. But, that reflects my taste, and it may not be yours.
Props for diving into a market that is pretty tough these days. I don’t have 10 LPs that I constantly play. You can see the warhorses by looking at what Chad reissues- he knows the market and what audiophiles buy. A lot of the offbeat stuff never gets reissued or is taken from a needle drop or digital file.
Happy hunting. Part of the process and joy of this is the learning and the search.