Honestly, just being hydrated with a proper meal before training should give you plenty of energy. Save money on taking anything else pre workout. I would get to the reason you are not feeling amped to train. Are you getting enough sleep, etc.
Inositol is just a b vitamin man. Yes b-vitamins are very important for energy production but they are very wide spread in food.
If you are going to supplement with b-vitamins, you should get a b50 or b100 vitamin supplement instead of a inositol supplement. It'll be around the same price and cover all your b-vitamin needs - not just inositol.