why these items? well first of all lets start with Berserker's Greaves
1. Berserker's Greaves helps teemo to attack quicker, this means that his E will reset faster and will deal more damage.
2. Malady
Teemo has a lot of burst damage when it comes to his E now you can deal even more damage with Malady why? well Malady passive gives Teemo basic attack to reduce targets magic resist so whenever Teemo attack a target this will trigger his E which will increase its magic damage.

3. Madred's Bloodrazor
Madred's Bloodrazor is a really useful item for teemo because as he attack, malady and E will go at the same time this means that he will deal TONS OF DAMAGE!!! (this is really effective to tanks)

4. Rylai's Crystal Scepter
As Teemo attack Rylai's Crystal Scepter will slow the target down this means his W will support him as he chase targets down, as well as his R will slow the target or even kill them.

5. Guinsoo's Rageblade
Guinsoo's Rageblade is pretty much one of the most important item that you must get why?
well first, as Teemo attack he will increase ability power and attack speed, this will help him in different types of ways first as he chase his target down his E will go stronger, second his attack speed helps him to kill the target quicker then before, and third you can use your Q as a finishing blow when Guinsoo's Rageblade is must stack

6. Guardian Angel
As you continue to deal damage to your target your E will poison them over time, so whether you die or not will still kill them, but if you die, while you reborn the poison will slowly kill them, so this make sure there dead before you are.

Try this build out and tell me what you think.