Improv studio while building studio

[mmoloch]

I will receive next week my first pair of monitors (JBL LSR305 with stands) and an audio interface, I have two empty rooms:

.1 - 2,92m x 4m
.2 - 2,15m x 4m

I have nothing to do sound treatment, well I have a sofa to put on the opposite side of the monitors, I did some tests with claps with and without the sofa and the sound became much drier.

Taking into account the monitors what is the best room? My main desk 2mx0,5m

At the moment I am not willing to invest in sound treatment because soon I will start to build a studio, just bought this house and I have a detached garage (4m x4m) from the house, for the moment the garage has a moisture problem and the winter started now, I will soon solve the problem of humidity with double walls and insulation which will also help with sound proof.

I also need help finding out what I should do/bluid inside the garage to have a good sound treatment.

Thanks