its been one day and diff is already ~ 80 . would i even get anything on a quad core i5 at this point ?
Difficulty is fluctuating up and down. It was up way past 100 at one point.
At 80, you'll find a block every few hours with an i5 quad core class chip. If you have the hardware, better to mine than to buy at this point. You'd only buy if you were speculating and expecting a big jump in price sooner than you could mine the amount you wanted.