I think that olaf is one of the best characters in lol.Also,I think that he is a great jungler due to his passive.

pros cons
1.Olaf is undefeated in late game 1.his spells are not so good
2.he is pretty good in early game too
3.his ulti makes him the best player for
team fights because he can escape from
stuns,slowed etc..

I got armor penatration for marks,hp for seals,magic resist for glyphs and attack damage for quintenssence.

I go 8 22 0 because I play olaf off-tankan I need hp and the defense masteries give me many hp.

I buy first lattern because I play as jungler.Then I buy attack speed boots.It and my passive boost my attack speed.Frozen mallet and Leviathan give me much hp that is useful in 5vs5 ranked.
Trinity is the key of the win because it gives you hp,attack speed etc and has a great passive and UNIQUE passive.Atma's is the engine of this build because it gives me the 2% of my hp to attack damage.Alos gives armor and critical change.finally I buy the bloodthurster which is ood because of lifesteal and close this build with force of nature or thornail.It's expected by my opponents.

I choose smite because I play as jungler and ghost because it boosts my movement speed.Apart from ghost I can choose flash or exhaust.They may help me in team fights.

Olaf is the best in team fight in late game because he goes first and he is undefeated if you follow my build.Also in early game you must focus your ganks on top.I say it because in bot is their support and in mid is his mage and he easily escape.