My favorite is ITC Vapes. I'm allergic to PG and this place is really good and pretty cheap too at $5 for 15mL. They offer 50/50 and Max VG. Since I've used them I haven't had any issues, and they have some really good flavors.
They say you should drip high VG juices, but I've been using the Max VG in a Vivi Nova for a long time and it works just fine. Just have to clean the coils after every couple tanks to keep them good.