It’s important to use all 13 tags and to add some variety (and avoid repeated phrases). Think about what makes your products unique and how shoppers might search for those items. You might have to get creative to come up with phrases that are 20 characters or less. If the keyword phrase you want to target is longer than 20 characters, adding multiple phrasal tags containing those terms can still help you match with those searches.
For example, let’s say your target customer is looking for “minimalist diamond engagement rings,” a very descriptive search that’s way more than 20 characters. Break the phrase into multiple phrasal chunks that a shopper might use in search, such as “minimalist jewelry” and “diamond ring” and “engagement ring.” These phrases are more descriptive than breaking up the keywords into single words like “minimalist” or “ring” but still contain all the terms that might appear in your target customers’ search.
Descriptive tags that clearly and accurately describe what your product is are a great place to start, but there are lots of different kinds of tags you can try.