I'm wondering how much turnips would give the most profit so I can know whenever I choose to buy some. So I want to know what the people here think of that question
The lowest amount Joan will sell turnips for is 90, the highest is 110. But like LambdaDelta said, it all depends on the selling prices you get to determine your profit, if any. I've bought low and had to sell for minimal profit. I've also bought high and gotten lucky enough to see an amazing spike and made a huge profit. It really is a gamble and there's no way to know how much profit, if any, you're likely to make in a week.
I second this. I don't think there's really a strategy for how many you should buy. It's really more of a chance based thing. Maybe buy less if she's selling them for too high of a price.