what will be a good beginner category to learn for Chrono Trigger for just starting out.

For a beginner I suggest the Magus%. It's only 2hrs long and you will understand all the meccanics of the game (glitches). In Jan 2017 we are planning a tournament for this category ;)

ps. Check here for more info http://ctt.neocities.org/index.html#infoContainer

learning magus will let you choose between 100%, (easier but longer) and No LSS, (harder but shorter) without any trouble, cause they're 99% the same.