But be VERY careful as the list above is for fruits and vegetables.
Non-organic meats have far higher concentrations of pesticides than all of the fruits and vegetables. And the highest concentration of pesticides is actually in non-organic butter.
So if you can only buy one organic food item it should be butter. Next priority would be meats and once those are addressed, you will want to focus on the fruit and vegetable list above.
Locally-grown organics are your absolute best bet, but bear in mind that many times buying locally grown food