In many cases, buying nutritional supplements is poor use of your money. If you eat a well-balanced nutritious diet and your workouts are not very intense or prolonged, then your diet should be able to supply all the necessary nutrients.
However, as you improve your abilities and move onto advanced levels, supplements are needed to help the body grow and restructure and to recover faster after workouts. Studies done with athletes have shown quite conclusively that the best diets will not supply the necessary nutrients or the amount of nutrients needed to help the body recover quickly.
Very often it requires 3 to 4 days before specific nutrients are fully replaced in the body following heavy workouts or severe competition. By using specific supplementation they are replaced within a day, it allows you to have quality workouts on the following days. However, the use of specific nutritional supplements should be based on the type of workout you do and how nutritious is your diet.
Note that many food products do not have the same amounts of nutrients when grown commercially as opposed to organically. Thus, it is difficult to compare the same product or to know exactly how many or what kinds of nutrients you are truly receiving.
For the supplementation to ensure that you have adequate amounts, be sure that you get nutrients that will be readily assimilated by the body. Thus they should be made from whole foods rather than synthetically. Do be fooled into thinking that you are getting whole food supplements if the packaging says natural without listing the foods from which it comes. In general, if it contains many chemical names you know that it is not natural. It should have foods listed that you can easily recognize.
For more information on nutrition and some of the specific nutrients that are needed in different sports see Build a Better Athlete, Explosive Running, Explosive Golf or Explosive Basketball Training.