Where do you buy marked scrolls from an NPC vendor?

Spell scrolls? They can be purchased from the white monks in Luna, in the room just southeast of the bank. They don't have all the spells though. You can also get them off of mobs you kill.

You have to get the rest from player vendors. I think only circle one through three are available from NPCs... possibly circle four, though more often you can only find one and two.

If you're on Ches, I sell them all individually or a pack with all of them, just NW of the Luna Bank on my pink lady vendors. I think it's not a common player vendor item though. But you do often see full spellbooks.

What shard are you on? If your on Europa I have a scribe, what do you need?

If you mean spells scribed with certain spells, PAlexanria is right. Circles 1-3 are available on NPC vendors and the rest have to be found through hunting (as loot on mobs, in t-chests, M.I.B.s, etc.) or bought from a player vendor. Or, scribe them yourself if you have a character with the neccessary inscription skill.

The most common ones that you will find on player run vendors are Recall scrolls followed by Mark, EV, and Ressurection. In my experience, at least.

If you are looking for something specific that you will be using alot of, ind someone with a scribe char to make them for you.

If you are trying to fill a spell book, Id just a buy a whole book from a player vendor. They usually run around 5k.