Rishikesh is where most people stop, and it is worth two nights – the evening aarti at Parmarth, the footbridges, and the ashrams that made the town famous. But the state proper starts above it.
Garhwal is the Himalaya without the Ladakh logistics: green, walkable, and reachable by road. The Valley of Flowers opens for about ten weeks a year and is exactly what it says.