New design project

Hi guys!, I have been asked to acoustically treat a room. The room has the dimensions L-5.1m W-2.7m H-2.5m.the walls are plaster on brick, the floor is carpeted over concrete and the ceiling is also plastered. I have a window 1.5m x 1.5m on the front wall and a door at the back. - What kind of treatment do you think I need? - Do you think a change in dimensions (with them being so nearly multiples of each other) is needed or just bass traps? I think, just some bass traps in all the corners and absorbers at the first reflective areas and opposite the window, like Ethan advises in his videos, should be enough. Oh, and just one more thing - Is there any truth in sound isolation is needed for acoustic treatment? I don't have a budget but it must be cost effective. look foward to reding your opinios.