Securely setting up a Linux cloud Server, hard to maintain?

Hello,

  Im am in need for a more cost effective host.  currently with certified hosting, basic semi dedicated, VPS if you will, it is managed by them.  I have found some attractive VPS plans with atlantic.net and sparknode for example. 

The ones in my price range are non managed, the ones that are managed are similar in price to what i have now.

I will be running clipbucket and i have a guide for installing the required programs and modules etc on a centos 6.x linux server, so im good there.  BUt i dont have any knowledge of how to install a firewall of if i need anything else to make the server secure from hackers etc...

Im a noob, really a noob with linux.  I have done some research and have found some companies that seem to offer a cloud server management service like dome9 and cloud flare, even rack space has a cloud monitoring service.  but im not sure of what i need etc to be secure.

so my question:

after my required script modules and php ffmpeg etc is installed on my server, which i have a guide for,  how easy is it to install all the programs etc required to make and maintain a secure server?

I would like to save the 30-40 a month on a managed server but also dont want to be getting into a lot of work as i have no experience with linux.  of course security is important.

ALSO are there any programs out there that you can install on your centos server that will manage security for me for a reasonable monthly fee?  i believe i have found some that will work but not sure if they cover everything or are what i even need.

whats the best option for price/ security etc?