Hi Rajat, July to March is the best time to visit Neemrana. The nearest train station, Ajaraka, is 17km away. From here, you will have to take a cab or auto to reach Neemrana. The main and only attraction in Neemrana is the Neemrana Fort (Rs. 750 ticket). It is open from 9am to 3pm. You can easily visit Neemrana and return to Delhi or head to Jaipur the same day. Yet, if you wish to spend the night in Neemrana then check out this page for accommodation options -
In addition to transportation, the ticket is Rs. 750 + food (Rs. 300, lunch and dinner). So, you are looking at around Rs. 1000 + transportation cost.