How Can I Make My Attic Livable for Furniture Without Roofing Issues?

We're planning to convert our attic into a cozy reading nook and lounge space, including adding a small sofa, low bookshelves, and some built-in wooden cabinetry. Before we start furnishing, I’m concerned about the roofing and ventilation—especially since the attic gets really hot in summer and cold in winter. The current roof is asphalt shingles with no ridge vent, just a few small soffit vents.

Would adding a ridge vent and improving attic insulation be enough to make the space comfortable year-round without overworking the HVAC? Also, should I be worried about potential moisture buildup affecting wooden furniture and upholstery over time?

Would love to hear your thoughts before we go ahead and set things up.