Firewall Help

Hello everyone
I got a part time work where a client requires me to setup a firewall .I need help with setting up Firewall ,I have little bit of IT background but i am not an expert. I really need this job for my growth/experience in IT and for some extra cash SO PLEASE GUIDE ME
So the scenario is
There is 1 head office and 2 stores in separate buildings with separate internet but Same ISP
Head office has around 22 PC's - Stores have around 10 PC's each .. so total of approx 40 PC's
The client wants
1.limit users internet access (facebook,youtube etc)
2. Client has a cloud based software and wants all the PC's to connect through a secure VPN to that software.

My Questions .
Which Firewalls should I buy that will be easy to configure ?
Is this a very difficult task or Amateur IT Support guy like me can handle it ?
A Little bit of guide on how to configure the cloud based software VPN and firewall setup

TIA
(Sorry for bad english ,not my 1st language)