Buying olive oil is tough, the industry is rife with oils that don’t contain what they say they are. Look for where it was Made in (not Imported from) and check for a bottling date to make sure you aren’t getting old oil.
See if you have an olive oil store in your area, these places buy in bulk and then bottle it for you so you should have the chance to taste the options. A specialty food store would also be an option, they are at least likely to know their product and can guide you to a choice that fits your preference.