I've been working on a campaign setting in general for fantasy RPGs, nominally with an eye toward D&D 5e, but also taking Pathfinder into consideration - being the game that the majority of my local acquaintances play. I'm mostly set as far as things like geography, history, mythology are concerned, but my primary sticking point comes from number 10 on the "Purpose and Style" list of assumptions about the D&D Multiverse:

10. Magic items are assumed to be available, and game balance proceeds from that assumption.

At its heart, I want this to be a low/uncommon magic setting, cast down from a formerly glorious age when wondrous devices and spells were commonplace, and enchanting items and weapons is largely a lost art. There will still be room for lost treasures and artifacts of heroes, but they would not be actively for sale or trade in even the smallest local economies. This presents me with something of a difficulty with regards to any potential martial players, as the bonuses and benefits for enchanted gear is part of how the game balance works at later levels, with regards to spellcasting classes that begin to hit harder and harder - even if spells above level 4 or 5 are considered to be lost, or otherwise exceedingly difficult to find and properly utilize.

I've chatted about this with a more experienced player friend of mine, and he offered me two potential solutions that both appeal to my particular sensibilities, but I am not sure how to rightly implement them.

1) Characters unconsciously enhance their own gear. One of the themes of my world is that every mortal being has the potential to wield magical power in some fashion, just not necessarily through spellcasting. This is a world that will include casters as well as unconventional supernatural power in the form of martial arts (monks). This method involves the slow awakening of the martial players' inner magic expressing itself by augmenting and altering their items slowly, adding more bonuses and possibly specific effects based on how they have been played and how they fight as they level up.

2) Maneuvers I was given a link to a third-party Pathfinder supplement called the Path of War, detailing specific maneuvers for martial heroes that have the same functional effects as spells, but are explicitly nonmagical (I'm reminded mostly of Combat Charms from the game Exalted, or any Martial Powers from D&D 4e in this regard). I'm not sure if I want to use this as it stands, largely because I want to stay as close to what is detailed in the core rulebooks as possible.

I'd love to hear other thoughts from more experienced players/worldbuilders on which methods might be better. Chiefly, what is making me hesitate is a lack of knowledge about what the Pathfinder system in particular assumes of player characters that have reached certain levels. How much of their gear is magical, and what specific bonuses are necessary to take on level-appropriate challenges?

My thanks in advance for anyone else's input :)