We always advise getting a domain name with a .com extension. Don’t choose .net or .org unless there’s a good reason to go for one of those instead.
People often won’t remember your domain extension and will guess .com. Also, many phones have a .com button on the keyboard. This makes it much easier for users to find your site if it’s a .com!
However, you might want to buy the .net or .org versions of your domain to prevent anyone else from using them. You can redirect these to your .com website.