Don't understand why you would only adjust one side.
A slack adjuster has a 'mile' of adjustment. You may have zero brake on that side. If increasing the pressure on the brake petal is not increasing braking action then your brake chambers may be at max throw. Not good!!! If you put new shoes on did they match the arc of the drums?
I would find someone qualified to work on brakes that will show you how to inspect and adjust brakes. There is more to it than cranking on the adjuster. One thing that should be included in any brake adjustment is a test drive and a check of drum temps. To tight is not good either.
Having spent many hours herding trucks around grain fields, the last thing we wanted was a tight brake setting fires, so we ran them on the 'loose' side. Just tight enough to hold with a full load on good slope. I have the habit of popping the parking brakes while still rolling a bit. If they don't hit with good authority, time to see why not.