Any advice on buying quality vinyl

I only buy original pressings that includes some Japanese first release pressings, mostly from 70s. Yes, I have just a few records that I would call Mint condition, most are strong VG+ and NM/NM-, and I have a few rare very playable VG records. Prices I paid vary from $0.99 to $150, about $30-$35 on average plus shipping. 

What Bill suggests would be a part time job and possibly big expenses. As for obscure musicians, anyone can play like Miles or McLaughlin ? Never liked Hancock, by the way. I stopped listening to classical jazz a long time ago too, though.

Hard to be sure what is the first run and what is not, I just follow catalog numbers.
If you are a good musician it is real easy to demonstrate it anywhere.
I even heard on youtube and a few times live in New York City some quite good street musicians. No recordings in most cases, I guess.
One homeless British guitar player on streets of Paris was most impressive - very much in line with fusion era Miles. Another was sax player on 5th Avenue, very deep into the blues.

Sometimes it is not really better/worse but different. As an example,  original US 360 sound and Japanese first release Bitches Brew by Miles. I like them both and listen to them both. Japanese vinyl is of higher quality, the records sound quieter and more balanced than the US pressing. But Miles's trumpet sounds a little closer to real on the US one. They are both original pressings in my mind. I tried a few re-issues including mo-fi and they all sounded worse. Didn't try Mosaic box release, though. Wish You Were Here sounds better on first release Japanese vinyl than on German, didn't try original UK, original US was worse than German.

In my experience all records sound a little better with each subsequent cleaning, even after three or four times. I use Okki Nokki machine and Audio Intelligent fluids, pre-cleaner plus three step solutions. 

udog, the last time I got Audio Intelligent fluids from Elusive Disc. I like those people. Soak with each fluid except water for 3-5 minutes before vacuuming off, regardless of how records look. When spreading the fluids with brushes for each fluid before leaving it to soak, I do 5 revolutions clockwise then 5 counter-clockwise and then again 5 clockwise. The same with water - final step, two times with water. I suggest Archivist for Step 2, it contains no alcohol. Good results, not the best but very good.
I soak for longer and multiple times if I feel that the record is very dirty, but this rarely happens in my case.

I seek out best pressings, in my experience they are all first release pressings either in the country of origin of master tapes or Japanese from 70s, and the best condition. Within reason, I always choose better sound quality over better condition. There are exceptions when sound quality is very close and slightly worse record is in much better condition and the music recorded requires that silence be silent. In other words, I don't want any clicks or pops or even soft crackles where they have absolutely no place to be. Example is Cielo e Terra by Al Di Meola. Japanese is best, I accumulated ten copies of this album just to have one almost perfect and another a small step below it. So, I ended up with four Japanese, one Dutch and five American. It was recorded in the US, and US copy sounds pretty good but no match for Japanese, Dutch is close to US, as I remember. I would sell eight copies that I don't need if it was worth it but as things are I keep them all.