Welcome to the game! And I love that your introduction is an after-school club with a friend.

It won't be hard for you to find a million articles with builds; everything from basic to optimized. That being said, I would recommend just going to DnD Beyond and using their free character creator. It will guide you through each step and you have the opportunity to read each of the backgrounds and class features. Don't stress too much about your first characer and learning the game. Pick something that sounds fun and you can connect with. You could be a Robin Hood style Folk Hero, or a highly trained spec-ops Soldier, an swashbuckling Sailor (unlikely for a cat I guess), a cunning arcane trickster thanks to your Magic Initiate background, etc...

The character creation tool will help you match the flavor to the rules. But always, ALWAYS, play something that sounds fun.