Thinking of doing a Shopify store

I have been doing alot of research lately about starting a Shopify store here online. I really want to do it but I'm scared about failing. I know there are alot of people talking about different ways of promoting an online store but I just don't know the best way to go about it. I mean I've read and watched alot of stuff about Instagram, Facebook and even Google adwords working best but does anybody have any true experience doing this? I was thinking of doing it based off people's pets such as pet jewelry. I know I have to find the right niche and the right product but it's got my head a little confused about where to start.

Any advice would be amazing thanks!