you know thse people that sell these traffic for example 10,000 visits for $30. Does these effect your ranking in any way, like does it increase ranking? Or it has no effect
Unless the people that visit your site link to it from their own, it won't have any impact on your rankings whatsoever.
It doesn't directly increase ranking, but if the traffic is legit someone is bound to link back to you. Paid traffic however is a total waste of money and won't give you better SERP's or good visitors.
My coworker bought these 10,000 traffic for his client, he knows these were bots because all stayed less than for second, anyway after the traffic was finish his client calls and says to continue the traffic as they have gotten four five sales from it, he thinks that somehow those traffic has increased their ranking, or maybe it was just coincident.
As I said before, it won't impact your rankings. And unless those 4-5 sales from the 10,000 visits are turning a profit (after factoring in normal expenses PLUS the cost of paying for this traffic), you should stop buying it - nothing makes a better case than seeing profits fall like a rock while expenses spiral out of control just before the bill collectors start (literally) calling. Speaking of bill collectors - I've dealt with them before. They're NOT friendly people.