I'm 20 and I really want to stop spending money on useless things.
Before you get into making money, go and live for 6 months to a year with very little. Recommend saving up a few thousand dollars, then go down to Mexico and try and make it down there on what you managed to save in 5 months. It helps to solidify your budgeting skills and makes you a better bargain hunter. When I was in my early 20's I used to go down to MX on $3000 for a 6 month stint. I didn't have much furniture in my house, just a bed, couch and a tv but it only cost me $150/month. I found out how to go to a farmer's market and buy food for an entire month for just $70. I learned how to cook for myself and even how to have fun by just exploring the city. Eventually you will even find out how to make money.
Then go back to America and you will have a new appreciation for money, jobs and what you can do. I honestly don't know what other people spend their money on that they are so broke all the time.
I buy only cheap clothes and THEY last me years. I still have all the cheap $5 fake soccer shirts I bought 10 years ago in Brazil. I still have a TON of $1 shirts I bought in China 4 years ago. 'Expensive' does not equal quality, it equals 'stupid'. If you want to find out the difference between expensive and cheap quality clothing get a T-Shirt Press and a Vinyl cutter. Now order a blank tshirt for $1, go rip a brand name logo off the net with photoshop and have the vinyl cutter do its magic. Press the logo onto the shirt (10 minutes) and voila you've just created a $50 t-shirt. Do you know the difference between regular jeans and stone washed? The stone washed have been thrown into a vat of STONES and washed. Instead of paying $10 for jeans you pay $400. Its really important that you go to the parts of the world that manufacture the junk you pay premium dollars for at home, it will open your eyes to the scam that America has been pulling on its people for 50 years.
$14 for a 30-pack of beer which will last you a night, at best a week.
or spend $14 bucks and get into a new hobby that you can re-use with your friends over the entire year. It will make you healthier, happier,, more social, more productive and more competitive in the long run. Beer will make you fat and lazy. Changing your hobbies, habits and bargain hunting will make you happier and richer without ever having to change your job. If you aren't down with University, look for small month to year long educations that you can get that will double or triple your income. There is no need to go to college when fixing cars or driving trucks will bring better money, faster. And if you were smart, you could vacation in Mexico or some other small country, 6 months out of the year on your beer money.