Dear Ruhl,
In general, supplements are mainly for convenience and to aid a more or less balanced diet. Supplements are good for a pure source of protein (apart from egg whites, but when you're having 30 egg whites a day this isn't particularly cost effective considering the prices of eggs these days). You do use a fast protein (like Primer) prior to working out to give your muscles a good dose of amino acids. Other than that, the vast majority of supplements out there are scams.
As for high carbs, I suppose your question really means what are carbs good for? They are good for anaerobic-type activity like weight-lifting. Without carbs, you won't be able to workout. Not properly anyway. They are good for inhibiting cortisol release during and post-exercise, and for this reason I'd be sipping a protein plus carb shake during my workout. Post workout, I'd have potatoes, rice, pasta, bread, bananas etc with a good whack of meat.
To finish, I'd list the supplements that are not scams. They are: protein powder, creatine, EFAs and some pro-hormones. You might also wish to read the Supplement FAQ and HST FAQ to better understand the principles of HST and the reasons why some supplements are must-haves while some are absolute rubbish.
Godspeed, and happy HSTing
