What should I know before setting up an ecommerce store?

I’m planning to launch my first ecommerce store, but I’m still trying to understand the best way to get started. There’s a lot of advice online, and it’s hard to know which steps matter most. While researching, I came across an ecommerce store setup service, and it made me wonder if it’s helpful for beginners. Has anyone here used one? I’d really appreciate your experiences and suggestions before I make a decision.