hey, most wanted profession would be the monk. the necro or the elementalist are also good to start with. you should try all the classes to see what suits your style. whatever you chose, use your common sense. read the skills and use them accordingly.
if you chose monk, you will be playing a passive role of healing or ptrotection for the most part of the game. monks are also good to solo farm once you get the hang of it. if you don't like to play as a passive char, then don't play monk :P
the necro or elementalists are also good professions to start with in pve. they usually play as offence. go for necro if u like to hex enemies or make an army of minions. the ele is also fun to play with since you get to nuke stuff and wach them burn
as for the campain, i would suggest you start with nightfall because you can get heroes to help you and you can find more ppl in the cities. some ppl are rude with begginers so with heroes you won't have any problems learning at your pace.
the best way to enjoy the game is to have all 3 chapters though. and remember this is a MMO so even if you play with heroes a lot, don't forget to interact with ppl. you will learn new builds and have more fun.
the pvp in this game is also cool. it's all organized except the random arena. so make sure you drop by random arena to see what it's like and then you can move on to heroes ascent, gvg or team arenas.
good luck
