Classes group together like-minded adventurers but these same characters may still vary greatly.
For instance, a Fighter may be a well-armoured, sword wielding knight, or a lightly-armoured bowman or even a club-wielding barbarian. A Priest might be a priest at a temple, or a shaman of a tribe or even a forest dwelling druid.
Don’t feel constrained by the Class options, let your imagination loose and choose whichever Class is closest to what you have in mind.
XP is awarded every turn. It’s estimated it will take roughly between five and eight real game-play years to reach level 15.