I would concentrate on digital painting as oil paints and brushes can be expensive. Just use the tools you have available. Good thing about digital is creating brushes.
And yes oil painting help me considerably, but that was the only media I was using at the time. My first oil paints only my granny liked but with practice, oh I mean lots and lots of practice anyone can make improvements.
I would suggest you practice for example on an eye, just the eye and spend about 6 hours on it pushing yourself to improve on it every step of the way. Then move on to mouth, nose and ears and then start again with another eye. But importantly, however move on to other things like leather, armour/metals, glass, water everything and anything. Focus on a particular thing and concentrate on it and zoom it to get the finer detailing, even although you will never spend all that time on on particular item when painting an actual picture, well some artist do but that is entirely up to you.