You start out with 50 points to distribute over the 6 Skills. Not every skill must have points in it. Every fighter starts out with a power level of 500. Whenever you're in a fight, you must power up in order to reach your power level and this is called the power up rate. Your ki is based on your power level, so the higher power level you achieve, the higher your attacks of ki can be.
Every fight is divided into phases and rounds.
There are 4 phases per round and each character in a fight has 4 turns during a round. Every phase is 1 second, that's why the actions of characters in the show are so rapid. Each clan leader will teach their pupils certain techniques. Cell may teach his pupils how to regenerated body parts. There will also be certain ki moves, which the character will learn from their clan leaders even though some ki attacks will be basic enough for the characters to know before hand.