This is a very loaded question, and not a simple one to answer.
Simply because there are so many places to
buy Nicotine. PG and VG. Also Flavors vary from brand to brand/ and from place to place.
But breaking it down. You can goto a popular place like Wizard Labs for your Nic.
Nicotine Extract
I usually get 250ml of the 60mg. ($21.29) Mix that down to what my husband vapes (12mg) I get 1250ml. Unflavored.
I buy a gallon of USP PG from Tractor Supply for $20 but you can buy it from the Wizard as well.
I buy my Humco USP VG at Publix for $2.69 6oz. (Or Walmart for $4) but you can get the VG from Wizard labs as well.
They sell flavors in 8ML glass vials for $1.49 a piece and that flavors a good bit of
juice.
You can also get flavors at other stores. OnestopDIY, or Ecigexpress. Or directly from the flavor companies (TPA or Flavor West).
But RTS also sells nic and a few other places. I personally rely on Wizard Labs.
DIY is more like an art form. so many flavors. Not enough time.