You can buy VG at places like walmart, like mentioned above, but Personally I find and VG/glycerin that is sold in the skin care section has a funny taste to it. Your better off getting VG that is used for baking, if you can find it. Baking VG/glycerin is what juice makers use to make eJuice, and it's alot better than the skin care glycerin. I don't know what it is, but the skin care stuff just has something weird about it that tastes off.
I order all my stuff on line just bc it makes it easy and you don't have to go looking for stuff in stores.
Check out BlueMist
vaping. They are an awesome juice vendor, but they also sell everything you need for DIY. I bought all my stuff there and it makes great juice. They have numerous options for nic base, an array of empty bottles and syringes/pipettes for measuring and mixing, and they sell a bunch of the extra stuff that isn't necessary but allows you to customize juices even more, like sweeteners, tobacco absolute, menthol drops and menthol crystals, ethyl mathol, and a liquid that you add to juice to give a cooling sensation on the exhale. They also offer the DIY flavorIngs for every pre-made juice they sell, which is awesome and is something very few vendors do, 250+ juices and 250+ flavorings for DIY.
I bought my PG and VG from there too and they sell them in 120ml bottles. I looked around quite a bit and BlueMists prices for their DIY stuff are pretty darn good. Some things are better priced than others, but the price of their PG and VG is one of the lowest I've found for that amount. They sell 120ml bottles of PG and VG for only $4 each. Obviously you can find a better price if you buy like a gallon, but personally I didn't want to have to buy that much, so I just bought 2 bottles of each. Getting 240ml of PG and 240ml of VG for only $16 isn't a bad deal at all