Here is budget data of Jyväskylä from the year 2011. It has been asked for by Antti Poikola. http://fi.thedatahub.org/fi/dataset/jyvaskylan-talousarvioluvut-ja-toteutumat-2011
It took some months to get it by requesting information.
Get some budget data
This is the first part. You have to decide what data you want and is it available.
In democratic countries there should be some kind of law about, how citizens are allowed to get public data about public spending.
In Finland for example you can make 'request for information' (tietopyyntö) about the data you want from the officials.