Organic foods have been produced without toxic herbicides, pesticides, and other toxic substances normally used in food production, so it's a way to reduce your body's total toxic intake. They can be expensive, but it's worth the extra cost to help maintain good health, or if you have illness, to help prevent further damage to your body.
I think all foods can be organic now.
Everyone's need for supplements is unique to each person. If fact, randomly taking supplements can sometimes be harmful, by throwing off your body's natural balance. Taking a lot of something you didn't really need can create a deficiency in something else.
Registered nutritionists can do tests for you to find out if you have a specific need or deficiency that should be corrected. They can also recommend the best balanced multi-supplements for your needs. It's important not to throw your body's homeostasis way off.

Another note about Organic foods - they are actually monitored by the USDA, so in order for a product to use the "organic" seal, it must be made up of 95% or more organic foods. There is also another labeling category called "made with organic ingredients" - to qualify for this label, the product has to be 70% or more organic.

It is true that organic foods are often more expensive, mostly because it takes more time and energy (i.e. money) to grow foods and raise livestock the "old-fashioned" way. For example, you have to pay a person more to weed a field than you would spend in weed-killer to spray the whole thing down, but then you'd be ingesting herbicides. So, there is definitely a growing trend toward organic items because you are ensuring that you are not ingesting possibly harmful products like herbicides and pesticides or medicines given to livestock.