Topics you need to understand to launch your business

In your business what are the topics, you would like to have more info on or you think need to understand better?
Can be anything: SEO, marketing, copywriting, finance?

I want to create case studies about business topics and would love to know what is the most important for you.

For me as creating a business is :
1 - Marketing - Even without a product how to start showing your work
2 - Copywriting - English is not my mother tongue so it seems I always feel short
3 - Productivity- With a small business, how to take the best of every minute and delegate with short of resources

Thank you