1. A source . A disc player ( DVD ?)
2. An AVR amp since you need a 5.1 channel decoder which will not be inside a low cost disc player.
3. 5.1 speakers. Least expensive route is to buy a 5.1 system from a company making speakers for PC use.
Look up Flipkart /Snapdeal etc. and make a list of the items offered. Then ask anyone on the forum if they are OK according to them . Then make an informed decision.