For Marauder, utilize your skill combination for increased damage and better tanking. Also remember to do your class quest as you will unlock important skills necessary for tanking (like Tomahawk). No idea about any decent guilds (it's called Free Company here) in Lich server but hopefully anyone from there can give you a help.

On gearing, be sure to only wear item that states GLD PLD MRD WAR only for left side gears (armors) (without LNC DRG at the back, those are only for lancer/dragoon and has lower defense rate) and equip VIT based accessories when you reach higher level, starting level 29.