Long before there were blackout blinds, we used 1" insulating foam, spray one side with 3M 77 adhesive and cover with tinfoil, shiny side out. Work wonders, and cheap. I use low-e and blackout blinds for the wife's benefit now.

An attic fan on a timer, or with a T-stat that pulls from your room will help. On when the sun goes down and or when T hits set point. But all told, you are looking at $300 or so if you have a well ventilated attic, which you might not have. A few bats of insulation above that room and foam the exterior walls are also good, but not cheap to foam.

The attic fan will increase the severity for those with environmental allergies like grass and pollen during certain times of the year.