Priority on Stalker's- Devourer, it helps to get it as early as possible to increase the damage it gains from jungling and kills,

One does not need to buy all of the early peices, but one can finish items as one sees fit. Buy the items based on what is threatening you

The red crystal is versatile, so it can be upgraded to finish whichever item you want to finish.

Replace Sunfire if there is no AD threat on the other team
Replace Visage if there is no Magic threat on the other team
Replace Fallen King and/or Mallet if you want to be more of a tank, or want an alternate offensive item


Hydra; Offensive item
Maw; Mix of Magic Counter and Damage item

Black Cleaver; Counter strong Armor Carry if you have a good AD carry.
Wits End; Counter to Magic threat
Omen; Counter to AD threat

CD reduction; Olaf has long Cooldowns, anything helps, especially early
Attack Damage; This flat damage is helpful early when jungling
Movement Speed; This helps one move around the map, move from jungle camp to camp faster, escape, and chase more effectively
Armor; This flat armor is helpful early when jungling

A mix of offense and defense. Be threatening, but also hard to kill.

Q and E are you main jungle spells. Q is more important because it has a lower cooldown and it does not hurt Olaf.

W is useful, but the majority of the lifesteal comes from missing health rather than points invested in the skill, and this build has good attack speed already when combined with Olaf's passive

R is free Armor and MR in the jungle, and it helps initiate when organizing ganks from the jungle.

Spam Q when Jungling
Try to get killing blows with E to avoid the damage penalty
Use W when you are at low heath

Use R when fighting a champ, it can be used to secure a slow when you have mallet or ruined king, and also provides nice damage, however it only lasts for one second so this is marginally impactful

As a jungler, focus on jungling until you are threatening enough, then continue to jungle to gain more threat and attempt to protect allies with your slow when you can, and also use this slow to attempt to secure kills by catching the enemy in a vulnerable position like a panther from the shadows.