I only buy nicotine base when it's on sale, and when I do I get 1000ml bottles. I then put it in an amber glass bottle and freeze it.
As for flavors I don't mind TPA flavors so I buy 30 ml bottles from good prophets. They normally are about 6 bucks not on sale so I buy the ones I know I like at any time. I buy a bunch of "new" flavors during sales to try.
Hope some of that helps.