I'm having difficulty finding spells for my characters. I bought some in Cyseal and I've found a few lying around but where do I go from here? I need the teleport skill!

Check with Cylia in the marketplace. She sells Air and Water spells. It should show up in her inventory. Remember vendor inventories change over time, so keep checking with her every so often.

Edit: Cyla is on the NE side of the market in Cyseal, standing in front of a blue tent.

Flynn

Cyseal:

The King Crab Tavern = Shereth (Upper floor) -> "Witchcraft" and Thievery spells
The market = Cylia the Enchantress -> Water and Air spellbooks

You'll meet Jahan at the first floor of Cecil's office next to the "King Crab" tavern. He is a wizard and better have him in your party!

Arhu sells Fire and Earth skill books.
Captain Aureus sells Warrior skill books.
The archery vendor in the marketplace sells Ranger skill books.
Thelyron will often stock a few random skill books.

Remember you can trade with almost all NPCs, not only vendors. Always click the trade button and you will quickly find people with spells.