How can i make characters(ex:-Emoji) by using JPG?

The best way to create a character in AE is to draw it directly inside AE using shape layer or create it in different software like illustrator or photoshop (i prefer illustrator) than imported to AE, also you can copy and past your character from illustrator directly inside AE and it's also a good way or you can use a external script can do this step more faster in better like https://www.battleaxe.co/overlord/  . so animated a character using still image like JPEG will be tricky and i don't preferred at all.

also to animate character it's better to use some external script like https://www.battleaxe.co/rubberhose/ or Duik https://rainboxprod.coop/en/tools/duik/ (this one is 100% Free)https://rainboxprod.coop/en/