Hi, I just joined this forum, and I'd be happy to help if I can. I took up knife-throwing a few years ago casually, in the woods near my house where no one would call the cops, lol. I tried all kinds of stuff, expensive and cheap, of all kinds of shapes, and tho I never became an all-encompassing professional, I got to where I could reliably chop the tab off a hanging coke can at 20 paces every 2 or 3 throws. I ended up learning not only about balance of the knives and weight, but also about durability and ease of maintenence once I started hitting them together with my grouping. Also, something of edge-retention, since I practised on aluminum cans, tree trunks, and an official foam target I bought from a sporting goods store.
I tried a couple different types of Hibben throwers, some United Cutlery "lightning bolt" throwers, some Ridgid double-edged throwers (not like they make anything else to confuse it with, or as of last time I checked, anyway), some smaller 3-inch knives I figured I could hide on my person, some leaf-shaped double-edged throwers from United Cutlery, cheap crap steak knives from the grocery store, triangle-bladed "needles" (yeah, right), the Cold Steel Tru-Flight Thrower, many assorted throwing stars, and just about anything else I could get my hands on that had blades on it.
Of EVERYTHING I tried, I eventually found what worked for me. The United Cutlery Lightning Bolt Triple Thrower set, with the shoulder harness
was amazing. They're constructed of double-edged 420 J2 stainless steel and came unsharpened, and the craftsmanship was blatantly cheap, but they were balanced PERFECTLY dead center and were a very comfortable size at 7.25 inches. I think I paid $25 for the set and they never let me down once. I did a lot of stupid stuff with'em, including, ahem, hammering them into a tree trunk so as to climb the tree, then hammering them loose afterward.... as well as throwing them into harmful targets I'd never touch with my pocket-knife, and I don't recall ever sharpening them. They never let me down, never bent, never broke, never chipped, nothing. And because of their balance, they helped me develop my skills easier.
Next has to be the Ridgid RG56 Double-Edged Throwers.
I believe they're produced by United Cutlery now, but they're identical. These knives were much larger, at 9 inches, and heavier. I don't have a clue what they're made of, but they're just as durable as the lightning bolt throwers, albeit with a slightly softer steel. They were also a joy to throw and balanced very well, but a bit blade-heavy.
United Cutlery also made the 3rd-place finishers I enjoyed. I cannot for the life of me find them online atm, but they're about 7 inches with a leaf-shaped double-edged blade on each, and I have 2 sets of 2 and their sheaths. They're also balanced wonderfully and fly great.
On the off-chance you want stars, then I HIGHLY recommend 5-bladed ones. I tried 3, 4, 5, 6, 8, 12 pointed stars of varying shapes. 3 and 4 blades don't stick well because they tend to hit on a "side" between 2 of the points. 5 and 6 are ideal. More points than that and there are too many points to hold the star easily if they're sharpened. Imagine throwing a circle-saw blade, trying not to cut yourself.
All the others I hated. I hated the Hibben single-bladed throwers I had, I HATED the Cold Steel Tru-Flight thrower (WAY too big and wasn't balanced worth a damn, and the cord grip quickly came loose of its glue and made holding it by the handle very uncomfortable), I loved the shape of those triangle-bladed "needles" but they were EXTREMELY handle-heavy and so didn't fly right. The 3-inch throwers I had carried no weight and didn't work well. The Hanwei "ninja shuriken" throwing spike set was surprisingly awful. I love Hanwei, don't mob me yet, hear me out. The armband sheath didn't hold them securely at all and the spikes themselves were a very odd shape. Imagine one side of the Cold Steel Torpedo (also terrible for throwing), except octagonal instead of round, and put a small cylindrical handle on it. I never noticed how well they threw because I was too busy noticing how easily they bent and the fact that they refused to stick due to lack of penetration. I tried to like them, I did.
I also had a set of actual throwing needles, with a very small diameter (think shishkabob sticks) and wicked points. Those I liked quite a lot, actually, but were damn-near impossible to find in the woodsy ground when I missed or simply pierced the target clean-thru. Also, being the nature of a round tip, they bent very easily and I was constantly very carefully straightening them with needle-nosed pliers.
Just from personal experience, beginner to beginner, I recommend that you pick a double-edged (not double-ended, unless you just want that), well-balanced, cheap thrower that you don't mind beating up. I HIGHLY recommend the United Cutlery Lightning Bolt Triple Thrower set, and the Ridgid RG56 Double-edged Thrower. Those are my 2 favorites. I don't recommend getting hung up on sharpening them, tho, if you're going to throw into a hard surface. Knives carry WAY enough psi to sink their tips in, even if they're very dull.
Hope I helped, and sorry for the text-walls. And I tried to post 2 pictures in there as references, but I'm not good with forums, so, we'll see how that works out...
~Grey