If you are concerned about security, just follow the "simple" steps below
https://www.digitalocean.com/community/questions/best-practi...
.. it's mostly just typing stuff in a terminal
You can probably skip 10, 11, 14, 15, 16, 17 (in the short run)
If you want to automate this, you can learn Ansible (or Fabric fabfile.org) but that is probably premature
Just make sure you have a backup of everything on your server (nobody is going to take that more seriously than you, specially for customer data)
For scaling, they have some simple Load Balancers now (pick the correct region where it is available) ... used to have to do some DNS-based load balancing before (AWS R53). Again, probably premature but it can be done without too much pain once you get there