K so at the start of the game build Doran's shield . Once You've finished the 1st route buy 3 Health Potions . After Finishing You're Second Route Buy Mandred's Razors ( Or Parts Of it If You can't afford it ). Finish Your Third Route and Buy Hexdrinker. After Your done with you're routes Gank Bot, Top, Or Mid for extra cash, and if the monsters re spawned do your routes. If You have enough cash First Complete Wriggle's and Also Complete You're Maw Of Malmortius, Then buy Frozen Mallet For Being Tanky, and The Black Cleaver For extra damage, with the passive effect of reducing your targets armor, and with your Ult's Passive that'll cause some good damage.

Why Choose Vicious Strikes?
It's Perfect for Jungling because It gives you extra Damage, and provides Life steal for a limited time only.

Then why choose Reckless Swing as your next spell to learn?
Because it provides True Damage to the opponent, this will help with Kill Stealing or getting the final Blow.

Olaf is amazing as a tank, you need the extra health for your Reckless Swing.
Also the armor will help from taking extra damage from enemies.