You may want a granular budget on your project. You can create a budget in Business > Budgets and then assign it to the project. A budget can be based on nominal codes or cost codes (or whatever you have named them to). You can then see the progress of the budget inside the project looking for any overspend. You can also use budget parameters in the approval and workflow processes with the over budget condition.
Give the budget a name and then set it to Indefinite.
As you can see we have three different nominal codes where we can spend different amounts.
Click next and commit the changes
Now go back into the budget and assign it to the project.
Remember to click next and go back through the budget again to save the changes.
If you now edit the project you should see the budget panel.
Now when you go to place an order and select your project and one of the nominal codes, the budget dot will show as will the budget progress.
After your first order has been created and committed, your Project should look like this: