Buy decent ones as you need them, my park tools, crank puller, cone wrenches are pretty nice, seem like they will last forever. As everyone else mentioned, get the open end wrenches, etc, from Sears or whoever has decent ones for cheap.

Also, look out for "substitutions" . . . that is tools that can replace a specialized tool. For example I use a vise-grip with a rag as a substitute for a lockring wrench, and a needle nose pliers for a pin spanner. I think the vise-grip works even better than the lockring wrench since it allows accurate adjustment, and stays clamped to the lockring throughout the adjustment, and so far, no damage to the lockring.