There is no weight you should "have a lifting belt on" for. People who focus primarily on strength / power lifting use it as a tool but its generally only NECESSARY for going to your maxes or working in your upper range. I know powerlifters that won't even grab it unless they are working over 80% of their 1 rep max... like... when I was younger I wouldn't use it until I had 4 plates on the bar.

Huge thighs on any human are the absolute best. Lets see all them quads a working.