Creatine can work, but it is an individual thing. Other factors need to be on line for it to do so, such as proper micronutrient intake (get your minerals). I get decent results from creatine, but one thing to remember is that it assists in providing energy for the atp -> cpk cycle, and this is at least a six second process in untrained lifters, and can be up to ten seconds. Lifts or sets that take longer than this will not really be affected by creatine supplementation, so there is no point in taking it the last week before a meet, unless you seriously need the extra water weight.
Creatine is very cheap, if you shop around. I get mine from
www.kilosports.com
Also, as I mentioned previously, proper micronutrient intake is a must, and it is very difficult to get all of your vitamins and minerals from food any more, with all of the nutrients that are lost in shipping, processing, etc. A good mulit-vitamin can go a long way.
Glutamine can help with recovery, and it is not that expensive.
These are the only ones I use, and I frequently wind up with free stuff to try "Hey coach, what do you think of this?" or some distributor trying to get me to buy something for my athletes. Most supplements are crap.
An eca stack can help with fat burning, as well as an NYC stack, and both are very cheaply made. You can get ephedrine very cheap, add a caffeine tablet, and a baby aspirin, and you are all set.
I have found very few other things worth purchasing.