Bottom Line: If you can't afford organic food, I would much rather you buy conventionally grown fruits and vegetables then none at all and turning towards fast-food, but with the many generic brands now producing organic products, sometimes it is the same price or just a few cents more than its counterparts. I always have my freezer stocked with frozen organic fruits/vegetable because they are cheaper and you don't have to worry about them going bad.
Dirty Dozen Plus (foods to try to buy organic-higher rates of pesticides): apples, celery, sweet bell peppers, peaches, strawberries, nectarines(imported), grapes. spinach, lettuce, cucumbers, blueberries(domestic), potatoes, kale, collards, leafy greens
Clean 15(foods that are less likely to have as many pesticides when conventionally grown): onions, sweet corn, pineapple, avocodos, cabbage, sweet peas, asparagus, mangoes, eggplant, kiwi, cantaloupe(domestic), sweet potatoes, grapefruit, watermelon, mushrooms