Since I'm using a domain, storm, that has several offensive mage spells, I chose spell focus evocation, along with spell casting prodigy. I don't want enemies saving against my spells and wasting half or all of my effort. You can still put a point or more into the heal skill so that first aid kits are more beneficial. If you have a high heal skill, you can cure poison and disease. Kits are almost always more beneficial than spells, but they cost gold. I just buy the cheapest kits and try to bump my heal skill every so often to keep it useful.