Olaf is one of those champions that is rarely played ( about 3~5% pick rate) and is underestimated. His Tough It Out lets him farm, lifesteal,and duel enemy champions quite well and his Reckless Swing gets through jungle camps and champions like a knife on butter. Olaf is known for Ragnarok because it denies all CC on him and can make for a nice gap closer with your Undertow since you can't be slowed. IF you have not tried him and think he's not that strong , give Olaf a go.

I use attack damage marks so I can deal more damage to units with my basic attacks and get some free AD to contribute to Tough It Out . This also helps when i'm ganking if I am building for a Wriggle's Lantern or a Spirit of the Ancient Golem. Attack speed marks are not as necessary since you have Berserker Rage

These runes are great against jungle monsters and other junglers. Scaling armor can work too but I prefer these since you need to gank pre 6 to get your items rolling and plus Ragnarok gives you 10/20/30 armor and magic resist.

This runes work well against junglers like Elise and Evelynn early and late game. This can also help your ganking in mid if the enemy mid laner is pretty strong. I however take only 6 of these and the reason is below.

This runes will help all your abilities come up quicker with 5% cdr at lvl 18 and 5% from masteries adding up to 10% in late game. I take only 3 scaling instead of 6 flat because junglers still need some magic resist.

You get even more damage on top of marks. Better harass and faster clear speed.

I tend to use 21/9/0 as it gives me the most out of his Undertow and Reckless Swing while it also increases attack speed and lower my cooldowns by an automatic 5% from Sorcery. Your E will always benefit from attack speed and cooldown reduction because of these masteries.

Note that Warlord is not taken. It is a neat mastery to have be honestly but Sorcery is slightly better because one of the goals in this build is to slam your enemy with Reckless Swing as many times as you can with some autos mixed in. Overtime your true damage will deal more damage because of its cooldown.

The starting choice for jungle with [health potion] this will later be built into madreds razors or Spirit Stone(Or both) depending on the mood of how you are feeling in the game.

madreds razors I would build this when my midlaner doesn't need blue. Don't be afraid about your damage because your masteries can back you up for a quite a bit of damage to still make you be able to gank.

I would normally build this when my midlaner requires the 2nd or 3rd blue buff. This item is great for sustain if you're having hp or mp problems and builds into Spirit of the Elder Lizard or Spirit of the Ancient Golem.

If I like to, i would take both for the attack speed and sustain as it helps me clear jungles faster to move on to next rotation(gank) although it may cost you a little bit more gold.

This is one of Olaf's best dueling items and one of the first you should get. It has all the stats you need on Olaf and a nice slow. Build a [[bilgewater cutlass] early and finish it later in mid or late game.

This item gives a good amount of damage and sustain through direct and aoe. Start building this for teamfights.

After Ravenous Hydra is when you need to decide to build tanky for the team or continue to roll on the enemy.

Continuing More Damage

Both of these items are god since they both provide attack speed, movement speed, and a chance to crit.

Gives a good amount of damage mixed with some survivility and a magic shield against enemies with magic damage.

Starting on the Defensive

are some defensive items you can consider when against an AD heavy team camp that is proving difficult.

banshees's veil are some items you can consider when against an AP heavy comp that is proving difficult.

This is my first guide, so I understand if it looks pretty bad and lacking of BB codes. But if you would like to give me advice, please do so. I'll try updating this as much as I can.