I was looking at How does focus work in dragon age inquisition? but this doesn't exactly answer what I'm wondering. Right now I seem to cap out at one whole focus bar. At that point I can use my ability. I know there are more abilities via perks, but what do I need to do to be able to actually gather more focus beyond the first bar?
You start out capped at one focus bar to fill up. The other two are unlocked by acquiring the Perks Advanced Focus and Master Focus. You will then be able to fill up the second and then the third focus bar, which will trigger the second- and third-tier effects, depending on how many bars are full.
In order to unlock Advanced Focus you need to have acquired 4 Perks in Forces. Master Focus is only available after having acquired Advanced Focus.