Merry Meet, Kristine!!
Good question. However, I’m not sure what you mean by “not overdo it each week”. Do you mean overspending?
When it comes to money management, I think you want a spell for discipline and focus. You may need to work with Mars or Saturn energy (Fire and Earth energy). Saturn is all about discipline and limitations, and Mars is all about willpower and motivation.
An easy way to establish some discipline would be to keep track of your expenses using an Excel spreadsheet or a similar tool (Google sheets has a template for it).
Whenever you need to spoil yourself, do it in a way that doesn’t require money, such as homemade baths, listening to music, drawing, journaling, calling a friend, or meditating.
An easy spell would be binding your negative pattern (overspending) to a positive behavior (an activity that is free). So anytime you feel like doing the first (e.g. online shopping), picture yourself doing the other one (e.g. writing). The idea is to trigger it when the other one comes up.
An old folk magic method is the following: When you get money, keep the highest denomination bill for as long as you possibly can.
Good Luck and Blessings!