Roltech hit on a very worthwhile investment. A voltage tester with a load. The [link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXWW16&P=ML]hobbico tester [/link] is great one.

There is not a single componant of an RC plane that is more important than a battery with a good charge. You can have a $5000 plane with all the best equipment, but if your $20 Nicad battery goes dead or runs out of charge during a flight,,, there is a 100% certainty that you will crash. A $25 voltmeter WITH A LOAD TEST is an essential part of your arsenal of goodies.... I would borrow one if you must, but its much better to have one of your own to ensure that your plane has the power to land safely. You should check your batteries between every flight.

There are a ton of goodies that you can use in your box like a set of ball drivers, glow plug wrench, extra glow plugs, small pair of pliers, zip ties, rubber bands, hemostats, misc socket head screw accessories, fuel pump, electric starter or chicken stick, tachometer, .... As was mentioned, see what the guys at the club have, they may have some things they will unload on you for free or cheap before you go spending a bunch of money.