/ic/ - Artwork/Critique

This is the first digital painting I'm making, and I'm doing this on photoshop with a mouse.

I used a photo for anatomy reference (I only changed her right leg position and made her spine I little longer because it was looking off), and another photo for the face (it was basically tracing here, just changed her hair).
The original one here on my photoshop is 5000x5000.

But I just did this tracing and I don't know where I go from here.

Should I start thinking about the base colors and shadows and highlights? I only know how to shade with a pencil, how would I go from shading in photoshop?
What other heads up can you guys give me, thinner lines?
Any other tutorials I can see for digital drawings?

I'm going to buy a tablet later in the year, I want to get serious about this.

This is the first digital painting I'm making, and I'm doing this on photoshop with a mouse.

I used a photo for anatomy reference (I only changed her right leg position and made her spine I little longer because it was looking off), and another photo for the face (it was basically tracing here, just changed her hair).
The original one here on my photoshop is 5000x5000.

But I just did this tracing and I don't know where I go from here.

Should I start thinking about the base colors and shadows and highlights? I only know how to shade with a pencil, how would I go from shading in photoshop?
What other heads up can you guys give me, thinner lines?
Any other tutorials I can see for digital drawings?

I'm going to buy a tablet later in the year, I want to get serious about this.