I feel like I'm spending too much. Please tell me how I should manage my money?

Something my horticulture teacher in high school always told us was that if we get a credit card and want to keep a good credit rating, don't go making a few large purchases, but make a moderate amount of smaller purchases. Reason being that if you're only making smaller purchases and you're good about keeping track of your balance after you buy things, it's harder to go over your budget and takes much less time to pay off, all the while keeping a decent credit rating.
Just remember not to let those small purchases keep building up. Moderation with your spending really is key when it comes to credit cards, I've learned.

His line of reasoning for teaching us stuff like this was that if we couldn't have an actual class for it, he'd at least do what he could to help us out.