The more tags you have, the more it will show up in search results.
One thing I found out is that using a tag common to a different template DOESN'T help. For instance the 40-something brunette shedding a tear "first world problems" template is very popular. But Imgflip tracks memes by template NUMBER. So if someone clicks a template and looks at "other captions", it will only track that template NUMBER. If you add a "first world problems" tag to a DIFFERENT meme you create, your meme won't be pulled up when clicking the popular template because they have different template NUMBERS.
Also, if you add another image Imgflip doesn't consider it the same template number.