I guess the most important thing is to find and set a specific goal for each bit of treatment you introduce into your room.
If you ask in this forum, this room is not purpose-built to be a studio and you don't want to spend the money for a professional make over, which is quite normal, I think.
So, forget all this measurement crap and the general "internet orthodoxy of room treatment" that is designed to make you feel bad about the looks of your room acoustics.
Do what you want to do in this room, get a feeling for what is hindering you to the get results you wanto to get, and go from there.
I have a music room that I teach, write and record in.
While recording and mixing I found it hard to get a perspective on the low mids, as I had a real pronounced room resonance around 130Hz (like, C on guitar and bass were really boomy).
So I made six 4 inch fiberglass panels (from one batch of rock wool) to put in the accessible corners in my room.
That tamed this shit enough that I am pretty sure that my mixes done here translate well into other rooms and other music players.
(I have the rule to not do crazy shit in the low end, though. You won't see me pushing 30 db of 30Hz on a moog taurus. I use P-Basses, Drop D at most, per DI or via miced amp, and I usually leave the low end alone, processing-wise.)
Then I had some flutter echo between parallel walls, so I found large wooden window shutters on my local craigslist that I put on one wall and the flutter echo is gone.
Now I am pretty happy with my room. It lets me make decisions I can trust, and I don't have weird stuff happening
Recording wise, when I listen back to my stuff, it's not that I think "wow, this room surely ruins everything"
(You can form an opinion here: )
I played, recorded, mixed in my room, found things that annoyed me, and did cheap little things to mitigate the annoyance.
Also your mic choices play a big role, here.
Some mics will record the light bub flickering in your neighbors fridge.
Find what works for you in your space, and that might not always the stuff they used on, you know, Pet Sounds.