NH8, which will take you Delhi–Jaipur–Ajmer– Beawar–Deogarh– Rajsamand–Nathdwara– Udaipur, has never boasted better road conditions than these days. This approx. 660km/11.5hrs journey is doable without stops in a day. But it’s better to divide it into two days.
Leaving at 5am, stop for breakfast at Old Rao dhaba (Dharuhera) before checking out the iconic Neemrana Fort-Palace an hour ahead. From here, I suggest a detour to Alwar. Visit the Alwar fort and the Siliserh lake. Once at Jaipur, stay at the budget heritage stay, Umaid Bhawan (from Rs 5,000). Next morning, leave by 5am and you should be in Ajmer by breakfast (try Honeydew), where you could also squeeze in a visit to Ajmer Sharif Dargah. If time permits, stop by the Shrinathji temple at Nathdwara (with its pichchvai paintings). At Udaipur there are a variety of reasonable heritage stays—Karohi Haveli (from Rs 4,200) and Jaiwana Haveli (from Rs 3,895).