Let me see if I can answer some of your questions.
Caulk gun.........used mainly for jerky (ground) I do not use it personally as I like the "rip" from muscle jerky
Stuffer.....depends on your budget and how much sausage you are planning to stuff. I have a custom "Kirby Canon" which I like but if I were to do it again, I would spend the bucks and get a 15# motorized vertical stuffer. LEM or Cabela's.
Grinder.....I have a 1.5 HP Cabela's grinder which I hardly use. It cost me a little more to have my butcher grind for me but I think it is worth it.
Hope that helps.
Lumpy