I don't spend a whole lot on records, and usually buy from a thrift store. I try to avoid records that are badly scratched(scratches between grooves, and very light scratches are OK for me, though) or worn out(the grooves start to look grey when it starts to wear out). Poor quality vinyl doesn't matter at all if it's in mint condition, sealed, or been played several hundered times; it still sounds bad. I try to avoid simulated stereo, although, most of the time, it just sounds like mono that has been slightly panned to one side or the other at a few frequencies, but once in a blue moon, one will be very bad or good. On a small label devoted to a particular purpose, simulated stereo isn't as bad as it can be, and is sometimes good. On the major labels, simulated stereo is often bad, and sometimes truly terrible.
I don't spend a whole lot of money on records, but I've found that original releases that aren't scratched and are reasonable quality vinyl(not full of impurities from recycling) usually sound pretty good. Rereleases on vinyl of records that were originally on shellac and aren't in bad simulated stereo are usually good(even though those releases were from the '60's-80's),
Really, cleaning records with windex damages them. Look up how to properly clean records, and follow the mildest method they say. If that doesn't work, don't clean your records.