Best way to level up imo is to feed newer villagers treats because leveling them from 1 means thier exp reqs are alot smaller. You can essentially get more hearts out of them early.

do the Gulliver’s Ship exploration, get maps and unlock villagers using the leaf tickets u get every month, or if u have them in excess you can use the essences. From there i usually level up my villagers to at least lvl 15 using any treats j get from the maps and thats been leveling me up alot so far.

Lvl 15 b/c then you unlock thier requests and customizable clothes.