Acoustic panel for room treatment

My audio room size is 15x30x8.
It is in half basement, as seen.

I am thinking of treating the room with some acoustic panels.
Any suggestion? How many? How big? Brands? Where in the wall?
Agree this is a huge topic. Would at minimum recc considering treating 1st reflections on side walls (both same side and opposite side speakers)  treating corners with bass traps... treating front wall with 4 inch panels behind your monitors. Absorb or diffuse in your back wall depending on far you sit from it.... huge topic I think GIK free advice would be best.