No one can advise you from this one inadequate photo. Post photos of the complete room. Skylights are not always the answer. Certainly, your dark walls are not doing this room any favors. They can create tremendous heat load in this room that will throw your HVAC out of balance. Can you add more clerestory windows instead?

And make sure they are installed correctly for the slope of your roof! Our last home had 6, all incorrectly installed, all leaked. Our ceilings were slanted as are yours. The light was wonderful, the heat loss not so much. And dealing with the leaks and damage...

Make sure you know if your homeowners insurance will cover the future water damage, or how high the premiums will be with the added risk. I would bet you have less than a 20 percent chance of not having future issues, since you are starting with a roof existing, that is not constructed for them, especially. Lovely space, consider adding a whiter shade of wall paint, and a some wall sconces?

One would be plenty. What direction does the proposed skylight face?

Properly installed curbed skylights don't leak. Period.

Like I said...

I need to see the whole space for sure .

Thank you all, I do think one will be enough in the space, It faces north and seems to get light all day.