If you're looking for cheap plinking bullets, the Win 145gr FMJs are about as cheap as they come. They have decent accuracy and they feed pretty well. Be careful with loading data, though! Do not substitute 147gr pistol bullet data, and think you'll be fine. The 145gr Winchesters take a lot less powder than their pistol bullet counterparts, of similar weight.
I tried some Hornady 9mm, 147gr XTP pistol bullets. They were very accurate, but they don't feed in the two rifles I had at the time.
I have also loaded quite a few of the 250gr Sub-X bullets. They are listed as .357" diameter, so I called Hornady to ask them about that. The guy on the phone said they have a thicker copper jacket, and the extra couple of thousandths diameter was needed to make them shoot accurately and perform correctly at subsonic velocities. I don't know about any of that, but they seem to shoot, feed, and perform as they should. They shoot accurately, but their point of impact is several inches lower at 50yd, than the other .350L bullets (and factory ammo) I've tried.
My favorite bullet for the .350 Legend is the Hornady 165gr FTX. They are very accurate and they have been the best feeding bullet I've used with the .350 Legend (but they still aren't 100% reliable in my rifle). They are one of the more expensive options for loading .350L ammo, but if I could only use one bullet for the .350L, this would be my choice.
I have found the .350 Legend to be a terribly finicking cartridge. I have struggled to get it to feed correctly, with two different AR uppers. Powder charges need to be pretty exact (especially with Lil' Gun); a 1/2gr increase can get you into high pressure signs, quickly, even before reaching the published maximum charges in the loading manuals! H110/W296 powders seem to be more forgiving, in this regard.
The overall length can be critical as well - a difference of 0.010" can make the difference between feeding correctly and jamming. A slightly longer COAL seemed to work better for me, for feeding reliability, than the published COAL numbers in the loading manuals. This seems to be the opposite of what I'd expect, but I can't argue with what I'm seeing.
So, I don't see the desire to use .357" pistol bullets, even if you're sitting on a large stash you're trying to burn up. I'd rather sell the .357" bullets, and buy specific .350L projectiles. The .350L is picky enough, without adding extra weirdness to the formula.