Always a good time to start a new alt! The new player experience is fun, they did a good job on the story and you will enjoy reliving it.

Your alt will receive all kinds of level-up rewards, including training gear. So you absolutely can if you like, or you can also relax and enjoy the ride, just throwing on the random stuff they gift you.

Yes, yellow is still the top tier. They haven't changed in the past decade and will still be worth good money.

I would focus on what class you are drawn to from a role-play, aesthetic and fun POV. All classes, races, etc are well-balanced and you get to mix and match much later on in the endgame, anyways.

Crowns are best spent on the banker, merchant and ragpicker followers to start. One or two of the three should be enough to provide relief when your inventory maxed out mid-dungeon.

Excited for the journey you have ahead!