You must duplicate the healing gem before giving it to either patient.
There is a 'cheat' you could use to get another gem (
Lost Items - guide and directory of inventory files; you would have to start a new game, visit the shrine, get a healing gem and save in order to get the necessary inventory files to transfer the gem to your current game). If you do replace the gem this way I would still duplicate it, in case the game checks for that later, rather than just checking if both patients were cured.
Over the course of the game, most warrior builds average 2 stat points to strength per level, 2 to agility and 1 to constitution. Especially near the start of the game, though, this will vary depending on equipment bonuses or requirements of what you find.
Mage spell books can be bought or found (I maxed Aura of Guarding and Spell Shield with purchased spell books, for example).
Free skills, and spell books you can buy (Spoilers)
You will probably want to switch to
restoration potions fairly soon, depending on how high your vitality is.
The Survivor's Instinct skill is kind of handy. It regenerates hit points too slowly to be of help during a fight, but it can top off your health when you are dropping off loot or trading with merchants, etc. Even with a couple weapon expertise, warriors tend to end up with lots of extra skill points, especially if you rely on spell books for any mage skills (though you need to be frugal near the beginning of the game, at least).
Elven Sight is much more effective than Ranger Sight, and the survivor's Curse spell is better than the mage's Withering Curse, but none of the skills are 'outright useless' (other than True Sight, which is broken). There are a few spells I consider
mostly useless (as in most games), but even then they can be handy in certain circumstances, or some people like them for their character build. Your best bet is to save before trying new spells, and see if you like them, or not.
