You always need to be aware of how much money you need to put on the side because of bills and things that you will need to pay, you also need to save a percentage of what you are earning.
If you manage to do only this and you are managing your money good enough.
Exactly, you must set on the things that you are going to use your money for. And I would say that just buy the things that are necessary and you really need. Don't buy the things that you just want to have it because you want it but buy the things that you really need so that you are going to manage your money properly.