Active abilities usually are on the left side of your level up screen.
So just for an "easy" example let's stay with spirit shield.
Even tho you play monk (I'll get to that in a second) lets take paladin as an example because they have an active and passive for AR.
Exalted Endurance is on the left side and an active, it will not stack with potion of spirit shield or even Gilded Enmity from Goldpacts.
Stoic Steel is on the right and will stack with anything.
Now the problem with deadfire, that to all rules there are exceptions, for example I don't remember 100% if the monk's modal for AR, Iron Wheel, actually counts as an active or not, I do think it does not stack but I don't 100% remember, and this is the case for many modals, unique abilities granted by items (which are named after abilities but do stack with abilities....).
You almost always have to test if something stacks or not, which isn't always reccommended on a TCS save (keep in mind, that in pillars games you can ignore TCS by simply loading a completely different save, this will not give you an exitsave, I would still just create a console toon for testing, its much more practical :P)
Brilliant recovers all resources including wounds (yes its cheesy)
I don't have community patch, but if you use a sc monk you "need" strand of favour for brilliant anyway, as the cloak doesn't last long enough without SoT or WoD.
So you should just use brillant from the gods and strand it, however a FF really doesn't need brilliant, you can either use hyleas talons or blunderbuss modal for resource regen.
Both merchants in Periki sell ingredients, there is also a gem merchant in Serpent's which you need for some recipes.
As to gearbefor Scordeo's sabre, I would just go for the pistol (pickpocket the key if you don't have enough mechanics for chest, lure merchant away from chest with spark cracker (just don't actually hit anyone with the cracker or they will turn hostile :P).
You can either wield the pistol in your offhand and with the right upgrades it will give you recovery stacking) or you can cheese it and just use out of combat with strand for infinite duration.
(not really necessary)
At level 17 you should be able to just kill fire dragon tho, don't you have resonant touch already?
All there is to the fight, keep dragon at distance with Dichtosmth Soul clones and hit the dragon with a blunderbuss for resonance stacks, once it has enough resonance to die just explode it.
Probably best if you practice this with a non tcs console exported clone of your char.
After dragon you unlock scordeo's sabre quite quickly, doesn't take much longer than 5 minutes. 😛