For a more detailed introduction to this guide please read the prot bis guide for the 10-19 bracket. I go into more depth there into stuff like what race you should choose and how to navigate these guides. So, without further ado, the best in slot gear for 30-39 protection paladins for PvP and PvE in Classic WoW.
Headpiece
Raging Berserker's Helm
Ravager's Crown
Brigade Circlet
Captain's Circlet
Lodestone Necklace
Sentinel's Medallion
Kaleidoscope Chain
Silky Spider Cape
Cabalist Cloak
Wing of the Whelpling
Ironspine's Ribcage
Archon Chestpiece
Polished Jazeraint Armor
Ravager's Crown
Brigade Circlet
Captain's Circlet
Neck
Gazlowe's CharmLodestone Necklace
Sentinel's Medallion
Kaleidoscope Chain
Back
Scorpashi CapeSilky Spider Cape
Cabalist Cloak
Wing of the Whelpling
Chest
Scarlet ChestpieceIronspine's Ribcage
Archon Chestpiece
Polished Jazeraint Armor
Dressing Room
If your focus is on Player versus Player action and if we choose from above the most useful in PvP (those that increase stamina, strength, armor, agility, and defense) then your toon should look like this: Protection Paladin BiS 30-39 PvP.
If you’re in a PvE mindset then with my chosen recommended best-in-slot items you would look like this: Protection Paladin BiS 30-39 PvE.
I built my Classic Protection set as a mishmash of both worlds centered around an aesthetic I find awesome: Protection Paladin 30-39 BiS Alternative Design.