Whenever you finish a challenge event, you will see a window that tells you how many points you made and the calculation behind that given score.
If your score doesnt change much, it probably means you are either not getting a higher Total score from that level, or that you are already pretty high in the rankings and getting a few extra points wont give you a huge jump on your “master score”
By re-doing a level many times with no item usage, you will hit a wall that will hardly net you a better score. The 2 biggest factors for getting a big score when going casual is getting a Chest killed, it will net you 5k points just for that. And not using gem respawns that will kill your score.