Some studies have strongly indicated that learning Esperanto as the first foreign language greatly facilitates the learning of a subsequent language. For example, in Finland students were divided into two groups: one took three years of German, the other took one year of Esperanto followed by two years of German. At the end, students in the second group knew more German and were more fluent in German than those in the first group. See https://en.wikipedia.org/wiki/Propaedeutic_value_of_Esperanto
I don't know how much that would help in languages beyond the first post-Esperanto language, but a positive initial experience with language learning would seem to be useful.
Some studies have strongly indicated that learning Esperanto as the first foreign language greatly facilitates the learning of a subsequent language. For example, in Finland students were divided into two groups: one took three years of German, the other took one year of Esperanto followed by two years of German. At the end, students in the second group knew more German and were more fluent in German than those in the first group. See https://en.wikipedia.org/wiki/Propaedeutic_value_of_Esperanto
I don't know how much that would help in languages beyond the first post-Esperanto language, but a positive initial experience with language learning would seem to be useful.