For a true newbie, a Warrior might be the easiest class. Like most games, the warrior class has a more straightforward, harder to mess up build plan. (See something, break something, not a complicate tactic).
For an experienced player new to EK, a Cleric might prove easier for the game. A decent Cleric build has the highest gold/XP accumulation per hour of game play (real world measurements), has healing and limited spell abilities. Some areas are tougher for Clerics (fire dragons for example) but undead areas that challenge other classes are a breeze.
Rogue and Mages are a little tougher for new players as they are squishy and require more nuanced builds to be effective, compared to a warrior.