Hi Kanedova,
You've already been given some good info here but I'll chime in with my

.
"PG + Flavor" only is the simplest, most cost effective means to taste test a flavor.
However I agree with the others that have already stated the addition of VG (and to a lesser degree; nicotine) will effect (usually by muting) the way a flavor tastes and at what percent it tastes best
to you.
So I am of the camp that you will get a better feel for your true "preferred" percentage if you test with your usual PG/VG mix. I would still omit the Nic if you are going to dump the testing sample once you are done with it as it is the single most expensive ingredient in almost every mix. However, if you plan to vape the left-overs; then you may want to include the Nic.
Since I started DIYing I have been an unashamed groupie of a member (here on ECF) who goes by
@Bill's Magic Vapor . He has mixed e-juices commercially and has shared a wealth of info on the hows and whys of mixing.
I mention him, because if you do a search for any one of his posts, you will see a link in his signature line. Click on that link and it will take you to a Dropbox of his that has a BUNCH of useful information.
For your question of this thread I would direct you to a specific PDF file in that Dropbox named "Flavoring Chart.pdf". If you open this and either print it off or copy it to your choice of reader it will give you a VERY EASY chart/table for testing any single flavor.
Starting at 5%, in a maximum of 9 steps, it will lead you in testing any flavor
up to 25% in roughly 2.5% increments. It is all done with drops (you will need to use the same sized eye dropper, pipette, or syringe for all liquids used) so it uses very little product, and it has done all the math for you so you just keep adding a few drops of flavor and PG as directed until you find that particular flavor's sweet spot. (Note: if you want VG and Nic in your test; just premix a small amount of a PG/VG/Nic solution as you like and use that solution, drop for drop, in place of the "PG drops" specified on the table.
This will not be a "perfect" percentage (I can already hear people saying "the drops won't be the same because of varying viscosity."

) but it will give you a really close/good starting point for mixing larger more accurate quantities.
If you have flavors that are too strong at 5% I have recently worked out the same "drops" steps to test from 1% to 9% in roughly 1% increments. I have that posted over on The Flavor Apprentice Flavoring Thread here:
The Flavor Apprentice Flavoring Thread
These numbers will simply replace the ones in Bill's chart. It is important to mention that this set of testing drops REQUIRES using a 25% DILUTION of the selected flavoring. That is explained in the post as well.
All that being said; there are probably as many ways to DIY as there are DIYers. This is just works easiest/best for me. Find what works best for you so you will want to stick with it. Don't ever give up!
Good Luck!!
PS: when you get ready to start mixing multiple flavors I would suggest you look in Bill's Dropbox for "Bill's 100DT Method Explained" doc that gives a really easy and economical method to create your own recipes.
https://www.dropbox.com/sh/lwfucwpf...k9qba/Bill's 100DT Method Explained.docx?dl=0