Get bane on your weapon as soon as you can. Raise your touch AC.
Other than that there's not much since you're set on your class, archetype, and weapon.
I've also been looking into the Wanderer, it's an interesting archetype. Doesn't give you much that would significantly change a monk build though, mostly a number of situational abilities that would be good to keep in mind for the times they're useful (being able to give the whole party pass without trace could be handy sometimes). I looked into combining it with Harrow Warden, which doesn't do much, but gives some useful abilities and I think it matches the general theme of a 'mysterious wanderer' quite well.
The weapon proficiency should be easy to get if you don't already have it.
Start investing in stealth around level 12 to use their nifty 'hide in plain sight' ability.
A general guide on monks should help you figure out a general direction on how to make sure you're a competent character.
As far as the campaign, do you mean you'll specifically be fighting Shadows often? If so, that can give you more specifics on how to prepare for those very annoying enemies. A Ghost Touch and Undead Bane weapon would be very useful. The feat Dedicated Adversary can give you a ranger's favored enemy class feature, but only against a much more specific group (like Shadows). Blind-Fight could be useful if incorporeal creatures are often attack from stealth or inside floors (and maybe Improved/Greater Blind-Fight, though I forget their exact effects).
before we try to make a build we need to dismatle what the Archetype truely is; a skill based, stealth Monk with a small amount of Bard abilitys.
Now, using Far Traveler to purchace Sansetsukon proficentcy should absolutly be your first step. It should be noted if 'Monk with a Sansetsukon" is the only rationale you have, the Sohei Monk also gets proficentcy for free, as the Sansetsukon is a martial weapon.
Combat Reflexes is a strong choice for your level two bonus feat.
Adding a second Archetype, specifically the Flowing Monk would give more of an "exotic warrior" feel, if thats what you're going for.
I'd like to give more advice, but I don't feel I have enough information on what sort of chatacter you are creating to really dig further.
I'd be happy to list more suggestions if you can tell me more on your concept