US$19.99 packs give the most bang for the buck. It is what it is.
Packs get richer as you cross over palace levels. e.g. 26, 31.
Watch for 'Holiday' packs containing (Multiple) 2 x 500 {x} candles. 1,540 candles to max out an Inquisitor. So buy for Sixtus, Ann, Vigo, and your troop type. [You'll only need to do this twice each and can then forget about such as you will have maxed things out.] You could buy for Adrian but you don't have to - you will have 1,000's of errands now or via packs; Errands get you order store Personal Points with which you can purchase Adrian candles.
Ann is not as frequent as the rest, just be patient - it will be some time before you can make much use of it, anyways. [Can work on gear needs in the mean time if you have all other gear needs satisfied.]
Sixtus and Adrian seem to always be in such packs, so any two should max those out for you.