Hi
The biggest problem I see in art is anatomy and perspective.
How far you take your studies is down to how realistic your artwork is going to be.
If you get the proportions and connections to the frame or skeleton right then you are halfway there. Think shapes at first but to get a likeness you must take measurements and keep checking them.
Even a 5 headed mythical beast will have a frame supporting it under the skin.
Good old practice is the key, no real short cut for that. If you use a reference photo try using tracing paper to check how well you did at the end of the drawing and work out how you could have done better. You will see what went wrong.
The 3D route is a quick start for a base image to work from but you need to be careful as images can have 'doll like' expressions.
The most important thing from all of this is that you enjoy your drawing
good luck and post some pictures if you need help

Tom