Can anyone tell me a few items that are fairly afforable that will give your pet a fair amount of stats? I don't want to spend too much, but I'd like to give my pet a little boost before tonight's battle.

Your best bet for boosting is probably the various Tomes you can get from turning in Mage Amulets to the Mage in Shadowglen. Buy about 20 or so for ~330-350k or under and in my experience you'll generally get a few more Tomes for that price than if you'd spent the same amount of pure on the Tomes directly.