It doesn't necessarily have to be that the ISP of your friend is bad. It could be that, if he's running it from a machine in his house, the computer on which the server is hosted needs an upgrade. If that's the case, either (a) buy a new computer, or (b ) upgrade the RAM in the current one so that the server can run faster.
When you first log into your Minecraft Account; desktop or browser mode, click: Options (on the homepage) > Video Settings > GUI Scale > Small. That should help it a bit. Also, make sure iTunes isn't running, because iTunes tends to make things slow, specifically Minecraft.