Attach a dimensioned plan of the 2nd floor that also shows the outline of the first floor, for the best suggestions.

Waht is in the 2nd storey ? It seems to be an attic space so often not living space . We need more info for sure . Once you have figured that then think about a nice grenn for the white trim and siding .Could you also post pics of all 4 sides of the home . The plan asked for is a must.

You have little room for a dormer that will look good. Between the gable and the chimney, it would have to be small. I suspect you'd be better off putting it on the back of the house, where, I'm guessing, you have one long, uninterrupted roofline. Then, you could put in a shed dormer, which would be wider than anything you can fit on the front.

One dormer on the front might get you light in your attic floor, but a long shed dormer, which you can't fit on the front will bring both more light and more ceiling height/useable floor space.

IMO wait until you tackle the addition since thta seems to be 2 storey so it opens into that attic space I presume So not sure what is going on inside that attic space Right now IMO adding dormers will be of no real help since where you need them is not where you can put them

I don't see how any dormers will work with the layout of the rooms and the exterior of your home.