Help understanding how to trade options.?

I am watching a company's (PCLN for example) hourly chart, and at 1:30 pm it's trading at ~$487, only to be down to ~$483 two hours later. Let's say I wanted to buy a put, what would be a good strike price? Because the option expires on Friday, how can one calculate the % gain if they were to only hold this stock for 2 hours. I understand that if I were to buy shares of the stock, I would have made around $4 a share, but because options have more leverage, how can we calculate the true percent gain? Thanks in advance!