I was in your situation and what I did was use GIK’s online resources and they had a sound engineer working with me. It’s basically free and relevant consulting.
On their website, you request a free recommendations/estimation and you submit drawings with measurements and photos.
Naturally, the more detailed your drawing(s), and the more photos you can provide the better and more accurate their recommendations can be.
I think this will give you a very good, if not final so at least a solid first, idea about what type of treatments, absorbers/bass traps versus diffusers, for example would be useful for you.
like many things, I think it’s the 80/20 rule – you can get quite far this way and then you need to spend a whole lot more time, money and effort to get further but the nice thing is that you can decide on that later, after you’ve taken this first step
Good luck.