Basically, you need to stop it from going idle.
In addition to the IIS Initialization module, you have 2 main paths...
1. Use an external "ping" service, to access a specific page every 10mins (or whatever)
There are plenty of these services available on the internet.
2. Use an internal "ping" IIS task to access the website every 10 mins (or whatever)
Personally, I took the 2nd path for our sites (still on IIS 7.5) and the sites are always responsive... but your mileage may vary.
There are lots of examples that can be Googled, but perhaps this might give you some pointers...