Hi
@Mactavish
@Frocket explained things pretty well but I'm going to toss my

in as well.
Maybe you or someone can explain what is meant by flavor ratios, does 20-30%, mean the final ratio of flavors to base? So if making a 100ml batch final total of ejuice, does that mean that 20-30 ml is flavors, and 70-80 % is the NIC base?
Flavor Ratio simply refers to the ratio of ALL flavors (whether it is 1 flavor or 20 flavors) to the total recipe volume (it doesn't matter if it is a 10mL recipe or a 500mL recipe). It usually is expressed as a percentage. So the flavor ratio is not related to the PG/VG or nic ratios.
I will also add a HUGE +1 to
@Frocket's recommendation to find a recipe/juice calculator you like
and use it. Then you will not really have to worry about which ratios effect what because the calculator will tell you.
I'm trying to keep it simple to start, and the helpful guy at NN seemed to suggest that flavorings were used in such small percentages that I could order my NIC base in the ratio of my final desired blend. I have not placed an order yet.
I'm afraid I have to respectfully disagree with NN Guy on this as a blanket statement. A lot of different people mix a lot of different ways. Some will mix with no flavors (and then NNG is absolutely right), some will mix with very little flavor and NNG is kind of right; as it depends on how much retweaking you want to do like
@MikeADore mentioned), and there are those who mix with lots of flavor (30% is not at all uncommon) in which case NNG is dead wrong.
It will depend on a lot of different things: flavors you use, brands you use, and ALWAYS; how
you like your juice to taste. That last one is the biggie. And only you can know the answer to it.
I'd like my finished juice to have a VG of 75%, PG of 25%, with a total NIC of 9mg. I just don't know how to order these 3 percentages for my starting NIC base.
I personally am not a supporter of premixing PG/VG/nic in bulk for a ready-made "base" if you are experimenting with lots of different recipes, AND you want a specific PG/VG/nic target at the end. It certainly can be done, but the individual recipe tweaking pretty much negates ant "time savings" you might start with in the beginning. By that I mean you are still going to have to break out the PG and/or the VG and/or the nic to get it to the 75%/25%/9mg you say you want.
Now, if you
know you will keep your Flavor Ratio at/or below 15%, and don't care what your PG/VG ratio is, and don't mind a nicotine range of 8-10mg, then yes, physically, it can be done.
For me, I say, use a nic in either 100% PG OR 100%VG along with some unflavored PG and VG, get and use a juice calculator, and start mixing. After a while, If you find you only mix a couple of recipes over and over, or they all have very similar flavor ratios, or you like unflavored, THEN revisit premixing a PG/VG/nic base. But, until then, you haven't committed a large portion of your supplies (and investment) to something that isn't working for you.
Or, if you just gotta try it; buy either 100% PG OR 100%VG along with some unflavored PG and VG, and experiment by making SMALL test batches of PG/VG/nic base of your own until you find a base recipe that works for you.
I am sure there are others that feel differently, and will chime in too, and their methods are just as right for them as mine are right for me. That's part of what makes DIY cool. We can tweak it and shape it so that it works for us.
I hope you discover what works for you. Best wishes.
