Gain setting is your main strength. The others I leave at zero as they are all canned effects, except for ABS effect I put a teeny tiny bit at 5%.
With my Logitech G25, I put 107% strength in profiler (spring, damper, autocenter all 0%) and Gain at 100%.
With my Thrustmaster T-GT, I put 65% strength in profiler (others 0%) and Gain at 100%.
As others have said, letting us know what wheel you use will help. But you can guesstimate based on your wheel's strength and my numbers above.
I like to mess with my wheel profiler setting first because I find the AC Gain is not granular enough, and it messes the individual car gains if I change it around too much (see below).
Make sure you do the full wheel and pedals calibration when you start AC for the first time. Especially the rotation (I use 900 degree). AC auto adjusts your wheel rotation to match the car's in real life, so if you don't set this properly everything will feel wonky.
Brake gamma is the linearity of your pedal. If you have a load cell set it to fully linear (1.0). I have stock pedals so I set mine to default 2.40.
Also, download FFBClip app from RD here:
https://www.racedepartment.com/downloads/ffbclip-app.7910/
Just read through the instructions, it's pretty straightforward. Basically AC also allows individual car FFB multiplier in addition to the Master Gain setting (can be adjusted on track with keyboard +/- button). What FFBClip does is adjusts this setting automatically to minimise clipping and give you the strongest FFB possible without losing information. There's several settings too if you prefer slightly weaker/stronger FFB.
Any questions just ask away. Enjoy the best driving experience this side of real life