Help me, /r/sysadmin. You're my only hope.

The title might be a bit sensationalized but I'm feeling extremely anxious and overwhelmed right now. I am here to ask for advice and recommendations and to bow my head, admitting that I fell in to a position that feels a bit over the aforementioned thing that brings my ears together.

I was contracted to set up a few computers for a small office (12-20 computers) on an existing network. I basically just had to patch some machines in to the existing network and set up the printers. The relationship worked out well and I turned in to their "on call" tech guy- mostly because I am way cheaper than some of the actual companies around here and can do most of the same stuff.

Fast-forward to the last few weeks- a lot of frantic texts about services not working and viruses. It was insane- hijacked browsers and ad ware abounding! I had mentioned how the DHS said not to use Internet Explorer and recommended Firefox or Chrome to them. I was later told that they "didn't like Firefox because it had so many ads that pop up".

I grew up on a computer and build my own gaming machines and even have a little fun messing around with Kali Linux and doing a bit of gray hat hacking on my own network. I am interested in this stuff and certainly I think it would be an interesting and rewarding career to be involved with IT and security especially.

So as you might imagine I kind of panicked because I'm pretty sure some of it was perpetuating itself over the network and I am only in the capacity for triage at this point. I really want to help - I am powering through the A+ book and have the security+ and network+ books waiting. I'm a book / tutorial hound and I just have to figure out how to harden this network when I can't write a security policy or lock-down each account as I would in a better managed network.

I am working a crappy dead-end day job and I would like to get in to this field but this feels like quicksand! I would love to be able to answer their questions about full disk encryption and walk them through setting it up!

If anyone could recommend their favorite ways to harden chrome or Firefox I would be eternally grateful. I really need some great ways to limit what each browser can get in to and some industrial strength malware / spyware cleaning tools. I used spybot and malware bytes but had some stuff today that was resilient even cleaning from safe mode.. I can't convince anyone yet to just let me back up essentials and format the drives.

I feel better just for writing this- I know it is all too common for things to be a complete shit show.

*Edit - Thanks for the advice all, I can get a clearer plan of attack now and propose / implement some changes!