So, I guess I am having a reading comprehension problem, but I don't understand how the Force Rating and Dedication talents are "ranked". If so, then you can bring your total Force Rating up to 3 buy getting both the FS Exile and Emergent talent trees( and buying your way to the Force Rating talent on both trees). I thought I understood that once you've bought a talent, you've bought it, and can't buy i again, unless it explicitly says it is ranked in the description.

Force Rating is ranked. Page 135 of the CRB, after "Ranked" it says "Yes."

By your logic then the talents Toughened and Grit can't be purchased more than once either and the rules allow for that to happen. You can only purchase a talent on a given tree once unless it appears multiple times in that tree or it appears on another specialization tree.

I think the confusion is between ranked and unranked talents. When you buy an unranked talent, then yes, you don't have to buy it again. If you purchase another specialization that contains an unranked talent that you've already purchased, it'll automatically be "purchased" once you have access to it, since it has a fixed effect that doesn't change with number of purchases.

Ranked talents are different. You must purchase each ranked talent separately; you don't get free access after the first. For each ranked talent you purchase, the number of ranks in the talent increases, as does the stated effect (more soak, more strain, more wound, etc.). So, the first purchase of Grit gives you +1 strain, the second gives you +2 strain, etc.

So there is a benefit to buying both Force Senstive trees? IE you can eventually get FR 3?

Yup. You get the fixed 1 FR from purchasing the trees, then get +1 for each Force Rating talent (ranked) that you purchase. Since each tree has one Force Rating talent, you'd end up with FR 3 if you buy both of them.