"Gustar" is not reflexive. The problem for English speakers is that we do not have a modern equivalent to its true meaning which is "to please". If you approach using "gustar" in the awkward but accurate meaning of "to please", it works. Example: "I like her." (She pleases me = Me gusta). "He likes you."(You please him = Le gustas). "We like tacos." (Tacos please us.) You will use the indirect object at all times because it is the act of being pleasing "to" someone. That also explains why we don't use "yo" or "tú" as the subject (because they're actually the objects). "Yo me gusta" is incorrect. A mí me gusta (a ti te gusta) is correct because whatever it is, it is pleasing "to me" or "to you".
It's backwards to English speakers; however, 300+ years ago, English did it the same way. The phrase: "He is my son and he liketh me." in old English is translated today as: "He is my son and he pleases me." Somehow "like" made the big switch to our modern usage and we diverged from the Latin use which Romance languages continue to use.