Hello and thanks for your question! Making your own tajin-style spice is a great way to use up citrus peels. Most recipes for this product call for three main ingredients: salt, ground chiles, and some kind of dried citrus product. 

For the citrus flavor, you can purchase dried lime juice powder online, or you can dry your own citrus peels at home and grind them to put in the powder. The classic flavor of tajin comes from lime, but there is no reason not to explore other citrus peel options and see how they impart different flavors to the final mix. Meyer lemon juice has a sweeter flavor than regular lemons, and the peel (reportedly) is a bit more floral. Fully dry the peels until they are brittle, and then make sure to store the final spice mix in an airtight container to prevent it from clumping and losing flavor. 

Michigan State University has a great article with some basic instructions on drying citrus peels here: https://www.canr.msu.edu/news/drying_citrus_peel_to_use_later

I hope this helps!

Jared