As Watchful said, just about any design with a point works well. As far as making throwers, if you have a grinder and some time you can make great throwers out of old lawn mower blades. The steel is soft and relatively easy to work with. It has always been my experience to start with a large blade first (10" to 14") to learn throwing techniques. Throwing large blades is much easier that throwing small ones. Most throwing competitions specify that blades must be a minimum of 10 or 12 inches, depending on which rules are being followed. A trip to a local scrap yard or welding shop may also help, as you may be able to find flat bar scraps for very low prices. Leaf spring steel also makes great throwers, but more time and elbow grease is involved. If you don't have the right tooling and basic skills the frustration factor may outweigh the cost of a new thrower.
Hope this helps. Good luck!