The Magicians question

If you want some classic character development, I would recommend going old school and reading Lloyd Alexander's Chronicles of Prydain. Disney butchered the series with the Black Cauldron movie, but the books are pretty solid. There are five of them and the main charcter progresses from being an irritating, self-important teenager into a capable heroic figure. And, of course, Princess Eilonwy is fantastic. Highly recommend!

Try the Belgariad series by David Eddings. The first book is Pawn of Prophecy. It should be just what you're looking for.

What you're describing is considered THE classic trope of the fantasy genre. Belgariad and Prydain are perfect examples. I'll also recommend Tad Williams' "Memory Sorrow and Thorn" trilogy, starting with "The Dragonbone Chair". It's a good time to jump in because he's coming out with a sequel trilogy soon.

You should definitely check out the Pendragon series by D.J. MacHale! The first book is The Merchant of Death. You could also browse the lists https://www.goodreads.com/list/show/5... and https://www.goodreads.com/list/show/2.... Hope you find something you like!

I don't know about a book but I think you would really like the series, GIRLS hbo.

Melanie Rawn's unfinished Exiles trilogy, Dragon Prince and Dragon Star trilogies, Jordan's Wheel of Time series, Dreams & Shadows/Queen of the Dark Things by C. Robert Cargill and David Farland's Runelords books all start with young, inexperienced protagonists coming of age.

I think the best comeing of age character building books are robin hobb's farseer books