With these items-build,you have from early game attack speed/damage.With,1. Malady your toxic shot becomes more effective,and 2. your attack speed and your movement speed(with Move Quick and Berserker's Greaves)are good for doing more kills.After,at late game you are ''improving'' your items, building items which needs the previous.Critical strike chance will help you a lot in minions waves or at when (passive:teemo becomes stealth if he stand 3 seconds without action, and when he is leaving from stealth he gain 40% attack speed) you combine your attack speed and your critical strike chance to spread more kills.

I hope you will like it...please comment if you have any problem...
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