im new in this things of Gameboards, so i know about the gameplay but i havent decided wich of this two games get first, which one is better?
It depends by your definition of "good".
They're quite different (apart being "one player VS the others"), so read rules, reviews, comments about both and then... choose!
How can you trust a bunch of random players more than your own judgement?
Is there going to be an expansion for descent?
Yes (but no date was announced yet. No big loss, considering how much "release dates" are worth when announced by FFG... ).