Short answer: there's no best. Lots of people will recommend you start at 50/50 and work from there.
Long answer: If you really want to know the ratio that works best for you, buy different ratios of a flavor you know you like (or are fairly certain you'll like). Start with something like 80/20, 50/50, and 20/80. Vape them and get a feel for how the ratio of PG to VG affects the vapor, flavor, and throat hit and see which one you prefer. If you wind up liking 50/50 the best, all you have to do is combine the other two bottles to wind up with more 50/50 juice! Otherwise, those juices make great emergency back-up vapes for when you're waiting on a shipment.
If you get sample sizes or go with a moderately priced vendor the cost won't be too high. Even if it were, you're investing a little bit of money today to find the type of juice you're really going to enjoy down the road.