I usually mix 10% RY4, Aplle... (for example: 1ml fl mix with 10ml vg) with mainly VG, may be less if your choice is PG.
Shake and wait for 1-2 weeks for liquid to steep, and enjoy.
This has always been a very personal issue. So try 10ml bottles with 5%, 10% and (or) 15%, 20% example before...