You shouldn't watch either as they are both terrible, but for your question FMA and Brotherhood are essentially different series. From the Wikipedia article, "Unlike the first anime, which had its own original story, the second series follows the story of the manga."
I, too, can read Wikipedia, I was looking for someone who is experienced in the series
And you think everything is terrible anyway so bugger off
You'd have to watch the origional FMA to follow Brotherhood, but it doesn't really make a difference which you watch first.
This sounds really contradictory
All I want to know is if I should watch FMA first or not, am I going to have trouble understanding things if I don't? Is it the best experience to watch FMA first?