3rd level fighter ~ extra armor training ~ take armored juggernaut. It starts as 1 dr if wearing heavy armor,increases to 3 by lvl 11 and increases to 8 by lvl 19.stacks with adamine dr.
Armor masters handbook pg 14 ~ paizo material
5th lvl stalwart~ fight defensively and trade the dodge bonus for upto 5dr that only stacks with class features . See above.
11th lvl improved stalwart. It increases to 10.
7th (recomended)bolstered resistance~double your dr to a max of 20 as an immeadiate action. Makes you fatigued next turn.
Combine with cord of stubborn resolve. +2 con and Never fatigue but take 1d6 subdual dmg per use. Ultimate equipment.
Material mastery and expertise pg16 armor masters handbook.
Special material Armor provides a bonus 2/4 times aday.
Adamantine ..... Half damage is converted subdual.
Dragon hide....dr 10 for type of dmg matching breath weapon.
By lvl 7 you could have 20 dr every round but also converting that incoming by half to subdual dmg. Unless your hit by 41 dmg your not hurt. But that does take a min of 7.5k plus 4k for crafting material to make your adamantine tatomi do.wizard friend withcraft wonderous plus using alternate craft rules for the armor ...dc30 7ranks 3 proficient 2 tools 5 crafters fortune 2 for friendly wizard hopefully +1int..total +20....pathfinder unchained pg 72
Granted it will take two years and many many beers for your wizarding friend.unless your using other cheaper materials below.
Dragon hide can be more easily enchanted for elemental dr
Eel hide provides 1 or 2 electrical dr
Elysian bronze dr 3 for heavy armor but only versus magical beasts. 1/5 the cost of adamantine.
Fire forged steel ..fire dr 2
Frost forged steel..cold dr 2
Ultimate equipment pg 50
Sunsilk add dr 2 /bludgeoning to any clothing or other armor
Qadira jewel of the east pg 33
This is a stretch but the properties are documented.
Mimameith...dr 2 / slashing or piercing. Also 5 points dr versus fire.600 gold per 5 lbs. Now the dm may not allow a shield of it, but making one shot paste is what it normally does dc20 craft alchemy check. Can find 1d4 doses free with dc 25 survival/herbalist check.
Ultimate wilderness pg 154
Take craft alchemy make the following with the alternate crafting rules(cheaper).
Fireward gel,frostward gel,mimameith, brawlers brew.
Educated drugist trait is awesome add 1 to the alchemical bonus(1 extra dr) of remedies and they heal 1hp.
Healers handbook pg.10
A little off topic but if you do get the above trait. Spam alchemist kindess for 2.5 silver piece per 1hp healed.thats 2 gold for curing 8hp. Granted it takes 10 minutes per 1 health. Chugalug that soda.
For faster healing troll stypic is also spam worthy. 25 gold if you make it. Heals 1hp plus fast healing 3(drugist) for 2d4 rounds. Averages 16 health per dose. But fort save is needed dc 15.adventures armory pg 24. This can be a cure moderate wounds in anti magic zones. Both of these will remove subdual dmg from the cord while healing normal dmg as well.