The Third Circle
The basics of rune magic is quite useful; the tattoo-mage can't use runic magic, but his magic relies upon symbols with set meanings or ones that have an obvious link to an effect. So he'll pick up a copy of an encyclopedia of runes, if one is present, or a basic guide to runic magic if there isn't.
"Yes, I suppose you can. Do you have any higher level tomes on tattoo magic, or grimoires about runes or symbology?" The elf's voice is surprisingly deep. "I would be willing to buy them, or possibly trade knowledge for knowledge. I have copies of my own guides and spell books I could trade." He slings off his rucksack, to make reaching inside easier if it's required.