This is my understanding of Teemo.

About Purchase:

Doran's Blade give you good recover at the beginning of the game. Plus the skill Toxic Shot will give you AD + AP damage.

Make the Runaan's Hurricane as the first weapo will help your team fight get the Maximization Damage as well.

Haunting Guise as the second one will give you good Survive Ability and AP damage. As the Major Equipment you should upgrade it to Liandry's Torment ASAP.

Nashor's Tooth always Teemo's Major Equipment, you know that, right?

Rylai's Crystal Scepter is a good option for your health and AP power up.

Frozen Mallet is the same above. It's good for against AD & ADC.

These Options I made are all for Balance.

AOE + 125+AD + 195+AP Damage----Damage output: 200,000+(Base) ~ 300,000+ (If you play well)

Hope you like it and enjoy.