In OS X, how does manually sandboxing an application from the internet compare to blocking it with Little Snitch?

I want to prevent inbound and outbound connections to one application. I can buy Little Snitch if it's the best option, but it feels like I wouldn't be getting much value out of it for that one use.

I've been trying to read up on OSX's ability to manually sandbox applications from functions you can specify. I'm wondering if this is something worth pursuing - meaning will it be as good (or more effective) than Little Snitch to block one application only, and how complex is it to set up for an OS X novice?

I've been trying to work out exactly how to go about this. 'man sandbox-exec' probably tells me all I need to know, but I need more dumbed-down steps of the whole process if possible.