Leveling up is the basic way to get them. You can sacrifice your levels to keep your level low so that you level faster and then use the mini game buffs to keep some strength while being level 0 all the time. Also using the essence to keep your levels while staying at level 0… A few quests will give you the blue ability crystal which gives you 10 skill points. Like doing the Lich quest and then talking the potion shop NPC after you kill him… But then a few dungeons give them as a more common drop like the ruins or the gator mine I think. You can also use console commands to spawn ability crystals, but that’s cheating :P