Is there a pattern to how skills are acquired?

There isn't a system as such, except for cases where certain skills require other skills. Each skill has a specific chance of appearing, and different factions have "favorite" and "unfavorite" skills. For example, for Knights, the chance of Chaos magic appearing is 2% (this is the minimum value in the game), while for Warlocks, this value is 15% (in contrast, this is the maximum value). For Summoning magic, the chance for Dwarves is 4%, which is quite low, so it's not worth relying on it too much. The probabilities can be found in the so-called "Skill Wheel." As far as I know, it's available in the file archive of our forum, and it also comes with the licensed version of the "Tribes of the East" expansion.