i bought him a $300 knife, he says we should stop talking

You made a gift, I'm afraid.
Your valuable life lesson (if they didn't ask for it, don't give it) cost you $300.
It most certainly could have been more (and it could have been a family member instead of a friend!)

Now, if they said, "Get me this and I'll pay you back" - then you take them to court.

Your "friend" is a douche. You don't stop talking to someone because they gave you a knife, that's absolutely fucking stupid. And I read your other story too, so I know he asked for the knife, which makes his reaction unbelievably stupid. And considering everything else he's done, he is 100% NOT worth your time. Regardless of what he or anyone else tries to tell you, you did nothing wrong. Remember that.

And I'd love it if a girl bought me a knife!

$300 is a cheap price to pay to know someone's real heart.

Can I be your friend? I want a a new car.

Ask for the knife back considering how that guy has treated and used you. But understand it may be gone and you'll have to deal.

I think that money is gone for good

He's not a friend or at least not the friend you deserve. An old saying goes something like this. Fool me once ( or use me once) shame on you, fool me twice shame on me. I hope you get your money back .good luck .

If he is really your friend he will understand and either pay you or return the knife. Maybe one of those expensive life lessons. I hope this doesn't jade you too much.

Did he ask for any of what you you gave him? If not they will be deemed as gifts , he don’t need to pay you back .