some advice:
if you play alone;
just go outside the town, kill monsters the same level as yourself using the staff.
when you reach lv4, press S and start level up your mastery for Cleric and Wizard.
add the fire, wind and earth attacks and use them to kill mobs faster.
if you notice you become stronger, go to higher monsters and lv faster but try to avoid party monster and giant monsters.
if the pserver have better sp than xp, you dont need gap, if the xp is same as sp rate, you should make a gap of 4, which means the difference between your own level and the level of the masteries you are raising. (eg: your lvl= 14; mastery lvl= 10; "gap4") you do this because gap4 gives more SP per monster kill than gap0. highest gap is9, which give most SP per monster.
if the pserver provide quests, you can do them. they are in towns, the npc have a scroll above the heads.the higher lvl you become the better skills you get, i suggest look for a guide which skills you should add for cleric/wizard. you dont need them all ofc, it also cost too much SP.
If you lvl in a party later on you can play either cleric or wizard. but you'll learn it.
have fun