Personally, I've become a big fan of
Bull City. Their VapersTek nicotine and PG/VG is very clean, and I like that they carry different brands of quality flavorings (Inawera is starting to become my favorite brand, especially the Wera Garden line). You get free shipping if you spend $75, and while that may sound like a lot, it's not too bad if you just stock up on stuff once and a while. I was in contact with them recently, and they're going to start carrying larger sizes of their PG/VG very soon (gallon was mentioned).
To put it into perspective, I primarily use an RDA with a mechanical, and I don't have to change my wicks often at all (using Japanese organic cotton). Before I starting using their stuff, I was replacing wicks every couple of days. Now I find I'm able to go quite a while without the need to replace them. I've been on the same wicks for about a week and a half at this point, and the cotton is still white and there's no gunk on my coils yet. I usually vape between 8-12MG a day.
I've been hearing a lot of good things about Nude Nicotine, but haven't tried them yet since I really like what I have found at Bull City.
Good luck on finding you match!