For basic cooking purposes, all you really need to get started is one large frying pan and one large soup pot or six- to eight-quart stockpot, both with lids.
You can accomplish almost everything with these two items. You can make soups, stocks, beans, grains, stir-fries, and blanch vegetables, sear meats, and sauté.
If you have the money to buy an entire set, go for it. It surely is a worthy investment. If you don’t have the funds, use the pots and pans you already have and add to your collection when you can afford it.
Traditionally, some of the best cookware has been stainless steel and cast iron, but if you don’t have either, don’t sweat it.
Just start cooking.
If you have aluminum pots and pans, it’s wise to use plastic or rubber utensils on them. Scraping aluminum cookware with metal utensils can cause some of it to leach into food. Aluminum toxicity has been strongly linked with Alzheimer’s disease, and other ailments.  Aluminum is a reactive metal, meaning it can react with acid or salty foods and release itself into the food product. Tomato sauce is an example of an acid food. If you are fearful of using your aluminum pots and pans, consider this: a person using aluminum-containing antacids (at about 50 mg per tablet) may consume more aluminum per day than someone using uncoated aluminum pans for cooking (ingesting approximately 3.5 mg per day). If you are eating antacids on a daily basis, you don’t have to worry about aluminum being leached from your pots and pans and going into your body, you’re already getting plenty of it from the over-the-counter and prescription drugs.
Cast iron is a good old-fashioned cooking choice, an ideal heat conductor, and can last a lifetime with proper care. Unfortunately, cast iron can be a pain in the buttocks as it requires special care and coating with oil to prevent rust. It’s also heavy to handle (literally), so you need strong arms and wrists – this would not be an ideal choice for the elderly, physically disabled, arthritic, or weak. A nutritional benefit of using cast iron: it imparts minute traces of iron into your food. If you are anemic (low blood iron), cast iron may be a great choice. Although, if you are anemic, you may not have the strength to lift a heavy cast iron skillet.
Nonstick coatings for cookware are hard chemical plastics made with substances that can emit hazardous fumes when heated at high temperatures. These fumes have been linked with cancer, birth defects, and many other health problems. A group of scientific advisers to the Environmental Protection Agency voted unanimously to approve a recommendation that a chemical used in the manufacture of Teflon (PFOA) and other nonstick products should be considered a likely carcinogen.  This is serious business. If you have Teflon or other nonstick pans, do not use them to deep-fry food, and do not place them under the broiler. Never, ever use metal utensils on them (spatulas, forks, and spoons) – it increases the likelihood that you will damage the plastic coating and ingest it. Carcinogens are not appetizing and do not contribute to long-term health. When cooking with nonstick equipment, use medium or low heat, quick-cooking techniques, and plastic or wood utensils.
I prefer stainless steel for cooking. It’s durable, reliable, lighter weight than cast iron, does not react negatively with foods, and is easy as heck to clean and care for. Just wash and dry – done! Stainless steel is also relatively inexpensive. And, there are many great deals out there (Stainless Steel Pots and Pans). This may be an excellent choice and can give you many years of great kitchen service.
Now… get your butt into the kitchen and rattle those pots and pans!