How to make it where my website can support a lot of people?

Right now it can only take 8 people simultaneously while keeping a 1 second page load time. Is this the host’s problem by not having a fast internet or is it my memory problem? My website runs on 600MB of RAM and 10GB of storage space. I am currently using 60% of my memory right now so It’s not a problem.
How do I make it where my website can support a lot of people?
Answer #1
Dedicated Server > Virtual Private Server > Shared Hosting
If I remember correctly your using cheap shared hosting. You could try by upgrading to premium shared hosting, which I think will solve your problem. I am using 1&1 and their servers can handle lots of traffic. My client with highest traffic would get anywhere from 20-30 people browsing the site at the same time, and never had any issues.
The best route, but most expensive, would be to get a dedicated server with an small SSD and good bandwidth.
Answer #2
If I were to register for web hosting at 1and1.com and chose the starter package, would I be able to have at least 20 simultaneous users on my site at one time and not have the website lag?