I would suggest this article named Can't connect to the iTunes Store found here http://support.apple.com/kb/ts1368.
If you haven't been able to connect to the iTunes Store:
- Make sure that your iOS software is up to date by connecting your iOS device to iTunes and clicking on Check for Update in your device's Summary page in iTunes.
- Check and verify that you are in range of a Wi-Fi router or base station. If you are on a 3G capable device, make sure that cellular data is turned on from Settings > General > Cellular.
- Check to make sure you have an active internet connection. You can check the User Guide for your device for help with connecting to the internet.
- Check to make sure other devices (portable computers, for example) are able to connect to the Wi-Fi network and access the internet.
- Try resetting (turning off and then on again) your Wi-Fi router
- If the issue persists, see troubleshooting Wi-Fi networks and connections.
Note: If connected to 3G, larger items may not download. You may need to connect to Wi-Fi to download apps, videos, and podcasts.
Note: All iPhone, and iPod touch models support 802.11b/g Wi-Fi networks. In addition, iPhone 4, and iPod touch (4th generation) support 802.11n Wi-Fi networks (2.4 GHz only).
And if needed there is a more advance troubleshooting article named
iTunes: Advanced iTunes Store troubleshooting