Nothing but respect for above vapors, but have to disagree on this advice. Remember they've been DIY for a while. Unless you have background in chemistry, etc. you'll learn a lot of lessons from early mixing sessions e.g. mixing on a tray or over the sink, turning off the phone, putting the cat out, eye protection, clean-up, etc. Better to gain some experience and develop mixing process using lower nic concentrations -- mistakes do happen.
Wizard Labs, for example, sells nic in 12, 18 and 24mg concentrations. If you vape VG juice, just buy close to concentration you'll vape, add 10-15% distilled water and flavors -- and vape away. If you want 12mg 50/50 vg/pg, buy 24mg of pg-based nic, an equivalent amount of vg, mix and add flavors. And, if you do the math (I have), there is no difference in the cost of nicotine.
The reason most use 100mg is for ease of storage/handling (e.g. multiple liters in the freezer) -- and because we've been doing a while. However, I suggest waiting until you're comfortable before mixing with that concentration. Enjoy and welcome!
