This completely depends on the person and circumstantial conditions. Some people have a lucid dream just a few nights after finding out about it (usually by accident), while some people can take months! If you do not get enough sleep or feel too stressed after work to try techniques, then it may take a long time, especially if you expect it to. It will also depend on how much effort you put in. However, everybody can dream lucidly, so try practicing with my how to lucid dream guide.