Is there any way for newbies to build reputation besides spending months to become a regular? Maybe some kind of a guarantee given by an already reputable user?
The rules clearly state how beginners to Legendaries go through stage by stage until they get a good reputation here, they are all full of challenges and struggles to achieve that, it's not as easy as turning the palm of the hand or like a magician.
For this reason, anyone can go through and get a good reputation here, of course not with guarantees, there is no guarantee for reputation, this trait grows by itself slowly or if you want to quickly gain the trust of other members here, Of course you have to do something that other members have never done before.
For example:
Solve puzzles or problems that other members cannot solve, whatever it is that essentially has historical views and value for the other members here.