Everyday Project Management is a great book. Jeff, the author, writes about the budgets and budgeting practices in the project management activities. You really need to learn this in detail. Project Management Academy, for example, has also a nice reference in its project management course. All practices and methodologies worldwide clearly express the budgeting process as not an optional activity for the project manager, so you cannot just skip it.
In this chapter, you learn effective approaches to budgeting, how to combine top-down and bottom-up budgeting techniques, how optimism stands in the way of controlling expenses, and the importance of building in some slack.