does my video evidence for runs half to be good qaulity because all i have to record is my webcam

you should be good as long as you point the webcam directly at the tv/monitor, although getting a capture card like an EasyCap or Dazzle would be useful if you decide to get better at the game.

Audio is the most important to be perfectly honest, as long as we can tell what's going on the video then your good, but audio is used to prevent splicing.