Minimal Setups
There is a temptation to treat minimal setups as a checkbox to clear before moving on to the more interesting parts of bullet journaling. That is exactly backwards. Minimal Setups is where a real understanding of the craft starts to develop, because the small choices you make about minimal setups reflect almost everything you have learned so far. People who skip minimal setups hit a ceiling within a year and cannot see why.
The other way round: time spent on minimal setups pays compound interest. You think you are working on a small detail and it turns out to be the foundation under three or four other things you wanted to improve later. If you are choosing what to focus on next, choose minimal setups more often than you think you should.
That is the short version. Bullet Journaling rewards patience more than cleverness, and almost all of the visible improvement in the first year comes from showing up regularly rather than from any single decision about gear, method, or collections. Most of what is on this site assumes the same thing: that you intend to keep at it, and that you would rather be quietly competent in two years than dramatically excited for two months.