If you're feeling like that is because you're not eating enough prior the workout
At 15 I would not recomend nothing with caffein
Make sure you're
1- Eating enough (get a meal within 3 hours prior to training) and eat plenty through the day
2- Sleep enough; Long nights talking on IM and having to wake up early in the morning is not good, 8 hours of continous sleep every night, otherwise you're overall performance will suck (studies included)
3- Creatine is not something that will make you gain mass fast, the usual gains associated with creatine supplementation are due to the increased intramuscular hydration (more water in the muscles). IMO (although I have not tried lots of supps) it is better to go with Pure Creatine Monohydrate instead of the creatine mixes some companies claim to be "the best creatine mix available". Pure creatine monohydrate is a lot cheaper and will get you the results you look for when buying creatine, wich is increased intramuscular hydration
"Short-term use of creatine in healthy individuals is generally considered safe (see Creatine supplements#Safety). , studies have not yet been able to demonstrate either long-term or short term creatine supplementation result in adverse health effects. Creatine supplementation utilizing proper cycling and dosages has not been linked with any adverse side effects beyond occasional dehydration due to increased muscular water uptake from the rest of the body. In fact, an increase in body mass because of increased muscle hydration is the most widely accepted side effect of creatine supplementation."
http://en.wikipedia.org/wiki/Creatine Print it and show it to your parents, if they still say no, then there's nothing you can do
Again, if you're looking for quick mass gains, creatine is not for you. Actually if that's the case, bodybuilding is not for you.
Creatine enhances the production of ATP, giving you
an edge in the workout. Nothing special about it