I gave some great leveling tips earlier in the thread.

The extra equipment should help alot, though.

The Ruddle in Rumina quest is available much earlier in the game, when you're still trying to leave Elicoor. You have to guide the two travelers to their destinations, and after you successfuly lead them to Kirlsa, you can buy the Blueprints item from Rumina. This is the only way to get them to recruit Izak (your original question), but by now, the sidequest's availability is long gone.

Don't worry though, it isn't exactly necessary...I've never really been fond of Engineering, and have never once recruited Izak over the course of the six or so+ games I've played of this game.