I'm no expert thrower, but I do have a good bit of experience, and I would say longer and heavier is what you want to start out with. Like at least 9-10" OAL. As you go shorter, it gets more difficult (at least for me) to throw consistently each time (short, light knives tend to rotate faster, and more rotations per throw introduces more room for error, at least that's my theory). My favorite throwers are like 11.5 " OAL. Also, if you want to throw no-spin, get something with a clean straight line down the top of the handle. You don't want guards or other bumps getting in the way of a consistent release. For instance, I bought 10 of these on ebay for about $30:
Deal spotting is a NO NO on this forum.
They're cheap Chinese junk. However, if you're just throwing them, it doesn't matter. They don't need to hold an edge, they're adequately pointy, and the steel is soft enough to withstand throwing. You'll need a vise or something to straighten the tips out when they get bent. They work well for spin throwing (I never throw beyond 25 or 30 feet). For no-spin throwing, I used a bench grinder to grind off the top guard and the top flange at the rear of the handle.
As for your suggestions, I would avoid to the Naruto thing and the throwing needles for sure. The needles cannot be spin-thrown, and they are thrown differently than knives (idk how to throw them). The other four links are too short or have guards. The design of that last set looks decent; I just would get something bigger that looks similar. And don't worry about sheaths for now. Figure out how to throw first, and then you can get something higher quality with a sheath if you decide you want to carry a throwing knife.
If you don't want to go really cheap, the next step up is probably Cold Steel. I don't have any myself, but I see their throwers recommended frequently.
Long story short, get something big and fairly heavy, with a simple design and clean lines. You probably want at least 3 of them for practice. Hope this helps
