If you are new to DIY eliquid , I believe that while TPA/TFA flavors are probably the least expensive to buy, they also are difficult to get satisfactory results with for a new mixer. Optimal percentages vary greatly within the line. Of course there are hits and misses within every flavoring manufacturer's line of product.
I highly suggest browsing the DIY liquid forum. Search for ECF member Hoosier and read the blogs he has posted. His blogs are a tremendous resource into the thought process and methodology in creating eliquid.
I've dabbled a bit in DIY and I would recommend to a newer DIY'er to start off with either Capella's brand flavorings or (and/or) the super concentrated flavorings offered by Vapingzone or Ecigexpress. The super concentrated flavorings will give you very good results with little tweaking if any, while still allowing you to add other flavors to customize to your hearts content.
This is only my opinion mind you. I'm not knocking TPA/TFA in any way. Do your due diligence of course and make your own decisions. While the super concentrated flavorings may seem a bit more expensive, the fact that satisfactory results can generally be had with 2-3% flavoring or even 1% flavoring for the super concentrated "gourmet" line from VZ, spending a little more for great results up front will be a more efficient use of your dollar in the very short run.Again, just my opinion.
Allow me to say that DIY eliquid tends to be an art. Everyone tastes differently. As it is, there are no hard and fast rules to mixing.
In general, be prepared to spend many hours determining your personal optimal percentage of usage for each flavor you buy from each company and be prepared to find out about the importance of patience. Most liquids take at least few days for the flavoring to diffuse into the base liquid, with some, (certain tobacco flavors) taking a month before they taste good.This is why I recommend the super concentrated flavorings or Capella's brand initially.
Good luck in your mixing endeavors.