Which Adventure for a Newbie?

Hi,

haven't been playing for long and having spent all of my starter gold from daily and unique quests on failed arena attempts, it is time to decide on an adventure to save up for. I failed to win more than once out of ten arena runs and feel that I wasted all the gold I spent on entry fees which I could've used to unlock two wings in an adventure.On the surface, Blackrock Mountain doesn't seem to reward half as many cards per wing compared to the other adventures so I guess that is a ruled out. I do like the look of the latest adventure especially because so many decks I face have a Prince Malchezaar which is extremely frustrating to play against for a newbie.So, which adventure should I unlock first?

Please help.

I didn't find the right solution from the Internet.

References:-
https://eu.battle.net/forums/en/hearthstone/topic/17614292186
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Thanks