Analysis

Dipper discovered the third journal, a book written by a mysterious man with a wisdom finger (totally normal). Since he found it, his doubs about gravity falls change into curiousity and thirst for adventure. Sometimes he succumbs to powers of the town, like the cristals, zombies, time travel, clones, the lilliputtians, BILL CIPHER... And this in spite of the author's warning ! But he realizes that is not a good solution, especially when his life is threatened, so he puts his mistakes right. Actually, he makes sacrifices for Mabel, because he hates to see her suffering (and this is reciprocal).  Their priority is to care each other.

Now, his main goal is to find the author. We can create a link between the author and him, in the first episode, Dipper wrote on the blank pages his own experience : He can trust some people, and particulary his sister, Mabel (plus, they don't come from Gravity Falls).

Dipper know there is a big secret about the town and he looks in a hurry to discover it, and  he's not totally wrong because Bill puts pressure on him about this fact (s1ep19 and s2ep4).

To conclude, I think Dipper is the one who takes risks, the one who will be in a dilemma and probably find the solution.