For neutral tone: Seagull or Ilford MGIV in Dektol.
For colder tone: Add 6-15ml of a %1 solution of Benzotriazole
For warmer tone: Forte warmtone in Zonal Pro at various dilutions or Agfa
Nuetol WA. Also Use the regular Forte with various
dilutions of selenium to provide tone or sepia tone.
Of course the best thing is to select one or two and try them and then over time get some sampler packs or minimum size packages and try different ones. I have a couple of negs that I use just to compare papers, developers and processes. Everytime I try a new paper/developer combo I get those two negs out first thing, make the prints and then file them away with notes on the back. Easy to compare differences that way.