I went there over 20 years ago so no point of saying anything about budgets.
However, if you get travel sick, I would strongly advice you to take medicines and precautions. One of my friends badly got travel sick and we had to turn back at a place called Kullu.
Roads are good until Chandigarh. Thereafter, its hell.
You also have the option of catching a flight from Delhi to Shimla but Shimla to Manali drive is the tough part.