IMHO:
1) The Bluebird box, if you can find it - contary to what many people have said, the remastering on this is brilliantly done - the problem was in the final EQ before release - just boost your treble and you have incredible Jelly Roll in great sound -
2) Library of Congress - the Rounder stuff has all the music but has, stupidly, cut out all the talk (Larry Gushee told me a few years ago that plans were afoot to release it complete, but were shelved when Alan Lomax died); get the Rounders, but find, if you can, the Swaggie LPs (though they may be expensive thes days);
3) Commodores - the best are the solo recordings, incredible stuff, in full mature flower, but the small group Comodores are way under-rated -
4) The 1923 solo recordings - really should come first, have been reissued in many forms - best sound is on the old Folkways LP with remastering by the late Carl Seltzer, but John R.T. Davies did a fine job also -