So far, as a matter of principle, I block those who offer -40%, which is the minimum Vinted allows (meaning if I could have offered less, I would have). From experience, people who make extremely low offers don’t even buy when you accept their offer anyway; it’s always those who offer a reasonable discount like 10% who end up actually buying.
Do you have a strategy for dealing with the idiots who offer insulting prices?
I don’t answer
and I move on to something else
it depends on the item and my mood, sometimes I put more than my starting price on them 
, sometimes nothing, I can accept sometimes
I’m trying to take it easy and not get annoyed 
I tell myself that if someone makes me an offer, it’s because they’re interested, so I have a little set phrase with a keyboard shortcut that says « Hello and thank you for your offer, but I can’t go that low 
I’ll make you a counter-offer anyway 
»
And for the days when I’m really annoyed, I just refuse, I rarely block people.
I don’t respond or expend energy on that.
I advise you not to block. In general, since it is allowed by Vinted, there is no really « legitimate » reason to do so, and in any case, you won’t see most of them again. But above all, there is the risk of encountering over-excited people who will make false reports that could get your account blocked.
I thought about this post this morning when I received a message « I’ll take it for €5 » on an item that was €50 new… I feel I have better things to do than waste my time. I sent a 
in response… and I’m moving on