Find accommodation near sanjauli or lakkar bazar. stay at ridge or mall would be expensive. search for hostels om bookings.com. I would advice you not to book hotel if you have time to search for a room. generally, prices quoted on the websites are much higher. you can bargain personally.
As you reach shimla old bus stand you will find huge number of people gathering around you to advertise about their hotel. You can choose one. They are cheap. And close to mall road, just a km trek.
I will give you a 100% hack by which you can book a good hotel at very cheap prices. You just need to book the room through OYO on the same day or 1 or 2 days before the stay. You will receive hefty discounts as april is not the peak season so less rooms get booked during april. OYO follows dynamic pricing which leads to very less prices. I have tried it many times. You can check now itself. See the prices of premium hotels in April and prices of today or tomorrow for the same hotel.
There are many sight seeing at Shimla.
Many cheap hotels are there in Shimla starting from 400 onwards.
You can book a cab for sight seeing. Happy journey :)
Hi Sushant, I have attached with this comment few options for you. You can click on the cards to know more about the hotels, you can use the same link to book these.