There are no recipes for Rappelz Rupees, and they don’t come from mob drops in the game

Apprentice I spells / Combat Arts are the default - when you gain a level you gain Apprentice I skills (you probably already know this, but I’m starting Rappelz Rupees at the beginning...) There are no recipes for these, and they don’t come from mob drops. 

After level 50 you do not automatically acquire Apprentice 1 spells; you’ll need to find a higher version as described below.

Apprentice II spells / combat arts can be acquired in two different ways - you can buy them off certain ‘trainers’ in the city zones, or you can buy them off crafters (via the broker or through personal contact with the crafter) that are having a rough day in the trade skill instances (it doesn’t take much to make these).

Apprentice III spells / combat arts can only be acquired through a crafter (Sages craft mage and priest spells, Alchemists craft fighter combat arts (essences), and Jewelers craft scout combat arts (runes)). 

These are a bit better than the App II’s but you probably won’t find very many; crafters that can do these usually just knock off an App IV instead. They do seem to be required for Trade skill Writs though (note - as of LU24, TS Writs are disabled. Hopefully this will be remedied soon.)