A single guy we worked with a long time ago was complaining that he never had any money. I finally said that if he wanted to pick what he spent his money on, stay home. Don't go to the mall, WalMart, anywhere. Go to work. Eat whatever is already in your house. Do stuff around your house, read, watch tv, whatever, but don't go anywhere. After a month, check to see how much money you have. You can't prevent people from sending bills, but buying gas, eating out, tends to fritter money away. Do it for a month just to see if it helps because getting a raise would give you more money, but it isn't happening often enough to make much difference.
I didn't expect him to actually do it, but he did. He said that worked for him.
My advice today would be the same except to stay away from internet purchases. It is now possible to stay home and spend money.