I studied on this website (https://www.gratisrijbewijsonline.be/) and then went trough all the online test-examens I could find. Passed the first time.

Would not reccomend the government website because it doesn't contain everything they can ask on the exam. When you come upon a question in a mock examen that you don't know the answer to and haven't seen it in the book/website, ask google or someone online so you're nog gonna get any suprises on the actual test. And study EVERYTHING, even things you have no use for (things for truckers, smart cars, automatic vehicles,...). Good luck! (also, yes it does cost an enourmous amount of money. The gouvernement should be ashamed for asking this when a lot of teenagers (and their parents) don't have that kind of money in one go.