The TYBW arc's starting chapter isn't a straightforward answer. It could be different based on the manga version and region. I suggest looking at dedicated manga websites or asking fellow manga enthusiasts for the exact chapter.
I think 'Fullmetal Alchemist' is a good one to begin with. It has a deep and emotional story, along with well-developed characters and beautiful illustrations.
I'd say it varies from person to person. Some prefer the original source, so they start with manga. Others like the immediate entertainment of anime. Maybe think about which format you usually enjoy more in general and make your choice that way.
I recommend 'Binding to a Taoist Master at the Beginning, I'll Become a God through Practice'. The main character of this novel, Mo Yun, transmigrated to a strange world that had been revived and was bound to a ghost-catching system. Although there was only one system, this system could allow him to catch ghosts, increase his Vitality Force, and increase his comprehension ability. Of course, due to his talent and the support of the system, he was invincible from the beginning. It's very exciting and interesting to read. I'm sure you'll like it. I hope you like this fairy's recommendation. Muah ~😗
I'd say it's up to your mood. If you're in the mood for a more immersive and solitary experience, start with the manga. But if you want immediate entertainment and a shared experience (like discussing it with others who watched), the anime could be the way to go.
You could begin at the beginning, which is a great way to fully understand the story's development and character arcs. Also, some people recommend checking out reviews or summaries to get an idea of what to expect before diving in.