With shared hosting, the resources you get are limited. Hostgator will kill your site immediately and send a 500 Internal Server Error message to your clients if more than the allocated resources are used.

I do not know your background, but if you are just starting up, you should still be able to use a shared baby plan to handle most of your traffic, till you see a gradual increase. The best way to go with is to host all your heavy weight downloads (product downloads, sales page images, etc.) on a CDN like amazon AWS and link from there. That should help you to hold most of your traffic using shared hosting. When you see an increase in traffic and subsequently an increase in resource usage, then you should look at moving to a VPS or dedicated hosting.