I'm a relative newbie at this point. After experimenting with lots of pg/vg combos, I find I prefer 70pg/30vg, its like the best of both worlds...the pg holds flavor very well, and the slight vg adds lots of thick vapor making the vape very satisfying and very similar to smoking an analog.
As far as flavors...it's so hard to tell, b/c flavor is sooo subjective as everyone says. Several vendors, such as tasty vapor, mister-e-liquids, diy flavorshack, allow you to choose your pg/vg ratio, and all provide flavorful high quality juices. I suggest you start with samples from vendors, in varying degrees of pg/vg, and pick a variety of flavors, such as fruity, tobacco, "desserty" pastry flavors, and you'll soon figure out what you like best w/o spending tons of time and cash on stuff you may not be in love with.
Personally, I prefer sweet vapes, so I lean towards mister-e-liquids french toast, bloogplanets ry4 cartos (sweet, burnt sugar creme brulee flavor), TV apple pie, TV banana nut bread, and the occasional tobacco flavors which are usually on the sweet side. Tasty vapor flavors have the option to sweeten them or not.
Start with flavors you love in real life, but also try some you are not sure you'd like. I've found some of my favorites are samples that vendors sent with my orders (which I would never have chosen by the way) have turned out to be my favorites. Good luck in your search!