You can add depth to flat surfaces by including contrasting diagonal stripes. How do you do that? Use masking tape to lay out lines that you want to paint. A roll will cost 20-40taka. A spray can of your choice will fil in the color you want. Cost of that is under 200tk.
Practice using a spray can if you haven't used one before.
Pro tip: Start moving the can in direction you want to paint before pressing nozzle. When pressed, continue moving. Let go cap while still moving hand towards other end of the surface to be painted. This will leave even payer.