Thanks for your query.
Mud and polythene is the cheapest solution for Roof Insulation available so far in Pakistan.Following are the ways through which you can reduce the heat exposure.
1- W.r.t roof, you shall go for ceiling option in 1st floor. Ceiling will help in reducing heat rates by 40%, you can have ceiling/ false ceiling around 55 Rs Per Sq ft in any city of Pakistan.
2- W.r.t Wall exposed to sun all the time, you need to give insulation sheet after 4" wall then you need to built 9" wall. This is the only way through which you reduce heat exposure through wall.