Reason I ask is, that a lot of beginners (myself included) assume that to make a strawberry custard juice probably just needs a strawaberry and a custard concentrate. Whilst 2 such concentrates might make a vapable juice, there is often a little more to making a good juice than just two concentrates. I would always recommend using a recipe, as can be found here.
https://e-liquid-recipes.com/
All The Flavors
Shake and Vape! - DIY Vaping Recipes
Find a recipe you like then go to a site like vapable and order the things you need. Just a suggestion.
You will probably notice that most recipes use a combination of different concentrate companies as each company has there good and bad concentrates. It's not often people use just one manufacturer for a recipe.