You should probably start with Character Creation.
The section Core Rules contains everything you need to know to play the game. The sections are organized in a suggested reading order for learning the rules.
Mass Combat contains an unfinished system for resolving battles with many participants.
The Monsters section contains the bestiary.
Attribute Check: 2d6 <= Attribute Value + Bonus - Difficulty
Expertise: Bonus 1 to relevant checks. Mastery: Bonus 2 to relevant checks.
If you dislike any of the rules described here: Change them!