Hi AchyGrappler and great question!
When to consider moving up a group at a track day? - 101
1. Have you got a good understanding and execution of the basics; throttle control, steering, vision skills, braking, body position, ect... ect... ?
2. Have you "really" learned the preferred line at "that" track. Yes, you can be a B group rider at one track and a C group rider at another.
3. Can you hold that preferred line at "that" track? Even if you get passed mid-corner?
4. Do you have control over your mind and competitiveness enough to keep the "red mist" in check? Knowing when to NOT ride or pull back a little is MORE important than most things.
5. Do you find yourself having to roll off or brake mid-corner to not hit other riders?
6. Do you find yourself having to constantly take alternate lines through corners while making/setting up a pass on another rider?
7. Have you got a second opinion? Friends don't count!!! Get a CR or coach to follow you for a few laps.
8. Can you recognize negative feedback from the bike? Can you recognize negative feedback from YOU... the rider?
9. Are you NOT afraid to ask questions instead of just "giving it a try and guessing what will happen?"
10. Can you recognize and understand that "the mix" of riders present at the track "that day" will be different than the next day, so... your pace and safety is relative to "the mix, that day."
11. Are you willing to make "ANY" compromise to ensure your safety and the safety of others? Both on and off the track?
12. Do you spend most of your laps having fun or considering rolling hot pit to give yourself more clear track?
Having helped many, many riders and a decent number of ninjette members move from C -> B or Novice -> Intermediate, these are my factors that tell me when a rider is ready. When in doubt, just ask a CR/Coach to do a few laps with you to give an eval. We love to be used and abused like that, it's why we are there.
Good luck, have fun!
Bonus: The bike must also be able to pass tech for the next group, so be sure and don't forget to check gear requirements. If the bike hardware is ready, then you can focus on getting that wrinkly gray matter inside your head ready.