Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
It has taken me a long time to figure out the best item setup for olaf.
You should notice few things that mastery setup, skill sequence and item purchase is 100%.
When playing LoL, you must look at the enemy teams hero setup for the best survivial build for your champ.
To figure it out, you ask your self:
Do they have casters?
Do they have dps?
Are they mixed?
If they are spellcasters, the Force of the Nature armor and Mercury's Treads is required for olaf to be an carry in the game.
If the enemy team have much dps champs, the Thornmail or Warmog's Armor can be good. The best movement boots should be Mercury's Treads
If the enemy team is mixed, the best setup would be Force of Nature / Warmog's Armor and Berserker's Greaves.