Here is an awesome article that prioritizes which fruits and vegetables you should purchase organic, including details on why.
For example, you should buy organic potatoes because they grow in the ground and have thin skin and therefore soak up all the pesticides. Bananas, on the other hand, grow high up and a have a thick skin and should be fairly well protected.
Cool stuff to help you save a little bit of cash while eating healthy. You're welcome, Mary. :)