You've probably heard that pesticides can have a devastating impact on our bodies. So, if possible, buy organic fruits and vegetables that have the highest amount of pesticides when raised conventionally. These include peaches, apples, sweet bell peppers, celery, nectarines, strawberries, cherries, pears, imported grapes, spinach, lettuce, potatoes, carrots, green beans, hot peppers, cucumbers, raspberries, plums, domestic grapes, and oranges. However, I don't worry about buying organic bananas, unless I plan on eating the peel!
If you can, buy directly from the farmer. Free-range eggs have much more nutritional value than the traditional cooped-up chickens can produce, but "free range eggs" at the grocery store might not really be any more nutritious than their competitors (and they will be higher priced!) This is because there are such lax laws about what constitutes "free range." So, if you can see chickens wandering around eating grass and bugs, and buy from that farmer, you're sure to get your money's worth and your body will get its nutrients. Also, buying directly from the farmer can save you a bunch of money, especially with bulk items, because prices are marked up in stores, and their products are fresher, and local!
Another option is to learn how to preserve produce yourself... freezing, drying, and canning... and then buy food in season and preserve it! I buy a half bushel of organic peaches in August when they are in season (through a co-op, which cuts me a deal) and then cut them up and freeze them in apple juice. I have frozen peaches to last me the winter.
There is no substitute for simply learning good nutrition and how to cook things from scratch. Unfortunately, you can buy all the organic cookies you want and still be unhealthy. The internet is a wealth of information on health and nutrition, although you can get bogged down in the "trends." My advice is to stick to advice at least 5 years old that the current experts agree on... and cook from scratch whenever possible. If you avoid the "trends," your pocketbook will thank you. And if you cook from scratch, you can often buy in bulk, make a large batch at one time, and then freeze/refrigerate meals to thaw out later. Consuming less meat is a good idea... most of us eat plenty of meat as it is, and it's expensive! If you can buy meat directly from the farmer, try to get the heart and liver as well. (They are chock full of nutrients!)