Not necessary at all if you've got a perfectly decked out diet.
Multivitamins are always good as insurance. There's always something or other that could possibly be lacking.
As far as supplements (the major being whey) is useful for pre/post training nutrition due to fast absorption rates, bioavailability & cost/gram protein.
That being said, having a "protein shake" as a meal is not ideal - a chicken breast/tuna or other source of lean protein is better.
Nutrition bars,meh, don't waste your money on them.