The Apple TV simply needs an HDMI cable to connect it to the Samsung TV. You'll also need to connect it to your home broadband via Ethernet or WiFi, depending on your router & set-up.
Just get a "High Speed" (aka "Category 2" aka "HDMI v1.3") HDMI cable, no need for "HDMI v1.4" and no need to spend ££££££ on fancy overpriced cables.
This will be fine:
http://www.amazon.co.uk/AmazonBasics...7884878&sr=8-1
For the DVD player, it depends on which connections it has. If it is an "upscaling" DVD player with HDMI, then get another HDMI cable. If it doesn't have HDMI, but is a "progressive scan" DVD player with Component video output, then get a Component video cable. If it only has a SCART output, then get a SCART cable.