I would start by making single flavor mixes to know what you are working with first. I always test TFA flavors at 10% to start. I have yet to find a TFA flavor that isn't good at that percentage. From there, you can mix the individually flavored juices to get more complex mixes. Adjust to taste.
Mixes I would try with what you have would be:
Strawberry Cheesecake - Strawberry, Cheesecake, and Graham Cracker
Banana Cream Pie - Banana Creme, Graham Cracker
Berry Crunch - Capt. Crunch, Strawberry
Strawberry Shortcake - Cake Batter, Strawberry
Gooey Butter Cake - Cake Batter, Caramel
The percentages of the flavors in the mix are up to you depending on what you want to be the primary and supporting flavors. Part of DIY is experimenting and finding what YOU like. Unless an individual flavor is just horrid, it's hard to make a mix that is completely unvapeable (which is why I say to taste the individual flavors first, just to be sure you like it).