Shiv,
The SME server is an excellent place to start. I would not consider using a NAS unless you don't intend to ever progress further. Your knowledge will improve over time. You can start out by just using the file sharing capabilities and then as your knowledge increases you can add further functionality.
Now.. To your configuration problem.You have not fully documented your network configuration. Please ensure you reconfigure your server using similar settings as your Router/Gateway.
Server IP address: 192.168.0.8
Subnet Mask: the same as your Router, could be 255.255.255.0
Gateway: This is your Router's address, could be192.168.0.1
DHCP: If your Router provides DHCP then disable it on the SME server.
If you have configured your server correctly you should be able to
ping 192.168.0.8 from your other PCs
Logon to the server manager using
https://192.168.0.8/server-managerIt cannot be stated too often for new users,
Read the manual, then reread the manual, I little perseverance brings great rewards.
You can make a start here
http://wiki.contribs.org/SME_Server:Community Remember: None of us start out running, we all walk first, most of us had to crawl.
Have fun,
Phil Brearley