Usually, if someone is just using their PC or iPod to surf the net, it shouldn't affect his gaming. However, if there's video streaming or something streaming going on, it can affect his gaming. There are a lot of things to help alleviate this:
1. Try and hook up everything by ethernet cables instead of wireless.
2. Get the fastest dsl or cable plan you can afford that has the most download and upload speeds.
3. Get the latest router (or gaming router) that lets you prioritize certain things like gaming as the higher priority.
There's probably more things but those are the top 3 off my head.