Press the Attack makes your enemy more vulnerable because after 3 hits, enemy takes more damage and you have more chance of winning against your enemy.

Overheal makes you survive longer. Since Draven doesn't have that much mobility, Overheal is a great way for surviving longer in lane or when getting ganked. Combining with the Bloodthirster, makes your rune more useful because it will make Draven take more damage from enemies with his shield.

Legend: Alacrity will provide you more attack speed when eliminate enemies. Since you won't be buying many items which give you Attack speed, this will give you just enough alongside Berserker's Greaves and Rapid Firecannon.

Coup De Grace will make you kill enemies with low health faster.

Nullifying Orb will give you an extra shield when you are on low health. Just rune is another perfect rune for surviving,especially when someone tries to ignite you.

Gathering Storm will give you bonus Attack damage.

2x +9 Adaptive force is really important because Draven needs more damage than attack speed in lane.

+6 Armor will make you take less damage from AD champions.

The Bloodthirster is a very useful item for Draven. It gives you enough lifesteal, more shield alongside Overheal and more attack damage. You should try to get this as fast as you can because it will help you in a lot of situations.

Berserker's Greaves is the best choice of boots for Draven. Gives you enough movement speed and attack speed. Take it as second item.

Infinity Edge is one of the core items for Draven.It provides you a lot of attack damage and gives you critical chance. The passive makes your critical hits more effective on enemies. Take it as either first or third item.

Rapid Firecannon is a very useful item because it gives you more poke in lane and teamfights alongside more attack speed and critical chance. Take it as fourth item.

Now here are some situational items

Mercurial Scimitar gives you an ability to remove all crowd control debuffs from your champion. It also gives you some attack damage, magic resist and lifesteal. Take this if the enemy team has a lot of Crowd Control.

Mortal Reminder gives you more armor penetration and Grievous Wounds on enemy champions. It also gives you some attack damage. Take this item if the enemy team has a tank and has a fast health regeneration.

Statikk Shiv gives you even more attack speed and critical chance. It also has an ability, when this item is energized, your next attack will bounce to 5 targets. Take this if you need more offense.

Guardian Angel gives you armor and attack damage. It also has an ability when you on low health, it restores 50% of base health and 30% of maximum mana after 4 seconds. Take this items if you need more protection for yourself.

Lord Dominik's Regards gives you attack damage and a lot of armor penetration. Take this item if the enemy team has a lot of tanks and shields.