One of the problems with lip balm is that it's very hard to make enough for base/flavor for just one tube. A single tube is .15 ounces, so making enough base from scratch for even ten tubes isn't easy. An accurate scale helps, but measuring .15 of this and .05 of that is kind of difficult. At the same time, I don't recommend making big batches, since then you might end up with 40 tubes of unusable lip balm. After making too many big batches that were no good, I needed to figure out a way to test bases and flavors without wasting too much. I use fancy carrier oils, so having those go to waste is not only sad, but costly. And while lip balm tubes are cheap, you don't want to throw more plastic in the trash than absolutely necessary.
For flavors, I figured out a decent way of testing them. I start by creating or melting down a small batch of base. I use the tiny disk clamshells from Majestic Mountain Sage, because it has a lot of room to stick labels with notes on them. I think something like these might work as well- they're cheaper, but don't have as much room for notes. I add a few drops of my flavor to the clamshell. In my case, single essential oils or essential oil blends, but this could work for testing out flavor oils, too. I add a small amount of base, and stir quickly to mix them in together. I then move on to the next flavor. Try not to have the base too hot- it might start melting the clamshell, and it could also weaken the flavor of essential oils with low flash points.
Testing out a base is trickier. Once you have a good idea of what you want, make the base, perhaps adding less of the ingredient you're unsure of. In my case, I'm trying to use candelilla wax instead of beeswax, because I want my products to appeal to as broad an audience as possible, including vegans. Since candelilla wax has a higher melting temperature, I don't need as much of it, but I'm not sure exactly how much I need. So I started with about half as much as beeswax, and the base into a single tube. Once cooled, I tested it, and determined it wasn't harder enough. I added a little more candelilla, and tested again. This time it was better- firmer, but not so hard that it's unpleasant. Once you have it right, you're free to flavor and pour into your remaining tubes.