Okay. You are almost where you need to be.
Waiting - Once you have a couple of mixes you like, make up enough of them to last 4 days to a week. Then, mix up some that you can let set for a week. Next week, break open that batch, and make more. The idea is to always have some waiting in the wings, steeping.
"Working flavors" - Try the TFA Vendor's Recipes document on the
Google shared drive. There are plenty of recipes in there that will get you started. I haven't found any of them to be bad. I still mix a few of mine exactly as they are in the document. There are some that I have tweaked to my own liking.
I used TFA Black Cherry as the one that I could mix "spot on" while figuring out some other flavors that worked for me. I mix it at 6% with 3% distilled water. It tastes great right from the start. It will get a little stronger as it ages, so if give it at least 3 days before changing the percentage of flavoring in the mix. I used to make it at 8%, but after a couple of days, it would get stronger and turn into a cough drop. Yuck. At 6%, it doesn't do that for me. TFA Orange Cream at 6% with .5% to 1% TFA Vanilla Swirl makes a tasty Orange Creamsicle that is pretty good right away, and awesome after 4 days. Again, I use 3% distilled water in the mix. It seems to "pop" the flavors, and helps keep my sinuses from drying out.
Good luck!