I looked around online but couldn't find a good guide detailing where the vendors who took Sequins (Solomon Island, Valley of the Sun God, and Transylvania) are and what they offer (specifically what QL gear they have). Initially I was content to discover them on my own as I progressed, but then I was irritated to discover that I would have been better off saving my Solomon Island sequins for the vendor in the Blue Mountain, rather than spending them in the Savage Coast.
2 Answers
Solomon Island
Don't waste your sequins at the first two vendors, it's not hard to run to the vendor in Blue Mountain as long as you don't dally on the bridge covered with corpses at the beginning of Blue Mountain (hint: they're zombies).
Kingsmouth Town (153, 375) don't buy stuff here!
blue QL3 gear
weapons, 146 power (40)
glyph, physical & magical protection (10)
glyph, penetration & crit (10)
lower left talisman, your choice of attack/health/healing (20)
upper left talisman, your choice of attack/health/healing (30)
Savage Coast (128, 854)
blue QL5 gear
weapons, 200 power (40)
glyph, physical & magical protection (12)
glyph, penetration & crit (12)
lower middle talisman, your choice of attack/health/healing (30)
upper middle talisman, your choice of attack/health/healing (55)
upper left talisman, your choice of attack/health/healing (55)
Blue Mountain (245, 643)
blue QL6 gear
weapons, 235 power (50)
glyph, evade & defence (15)
glyph, crit (15)
Valley of the Sun God
No skipping ahead here. Roads are only moderately dangerous, but it seems like you need to progress the story mission to gain access to the second zone.
Scorched Desert (601, 436)
blue QL7 gear
no weapons
glyph, penetration & hit (17)
glyph, evade & block (17)
lower right talisman, your choice of attack/health/healing (30)
upper right talisman, your choice of attack/health/healing (55)
City of the Sun God (400, 52)
blue QL8 gear
weapons, 282 power (50)
glyph, physical protect & defence (20)
glyph, penetration & crit (20)
Transylvania
The roads around the CoV Envoy & Agartha entrance in Besieged Farmlands have mobs on them, otherwise travel is pretty safe if you stick to the roads.
Besieged Farmlands (1007, 1035)
blue QL9 gear
no weapons
lower left talisman, health (30)
upper left talisman, healing (55)
head talisman, attack (65)
Shadowy Forest (853, 872)
blue QL9 gear
no weapons
lower left talisman, healing (30)
upper left talisman, attack (55)
head talisman, health (65)
Carpathian Fangs (710, 681)
blue QL9 gear
no weapons
lower left talisman, attack (30)
upper left talisman, health (55)
head talisman, healing (65)
From memory:
The Sequin Vendor for Kingsmouth Town is just north of the police station; the one in the Scarred Coast is next to the fish and tackle store, and the one for Blue Mountain is in the main building of the Wabanaki Reservation.
The vendor for the Scorched Desert is in Al-Merayah, next to the Council of Venice representative for the area.
In the Besieged Farmlands I think you can find the vendor in the inn, and I'm certain that the vendor in the Shadowed Forest can be found in the Draculesti camp.
They're marked with a blue-on-white pile of coins on the map, and in exchange for sequins of the appropriate area they sell blue grade weapons, talismans and glyphs of a quality level appropriate to the area.