I would start by learning 3-2-3, assuming you use either FreeSlice or some other edge pairing, and while practicing this you can work on this you can work on the fundamentals of Yau.
In doing this I went from 1:45 to 1:12 (my current average)
assuming you use the CFOP method...
Buuut... if you use the ROUX method then . . . . . . . . . . . . . . . .
Learn the Meyer method for 4×4
(or HOYA, it's also a good one))