Quote Originally Posted by Atreides
Counter fire their arrows with 'javelin dedicated' of archers.

Use all you have to slow them down.

I recommend you to bring 'javelin dedicated' troops against the chariots. They can return fire and got a special bonus against chariots. You can recruit either Velites or Light Auxilla. Near Egypt their are always 'javelin dedicated' troops as mercs available. .

I second the suggestion of Velites or other skirmishers. They're cheap and make good fodder. Plus, with their formation (more spread out than normal infantry), it's harder for chariots and cavalry to break completely through their lines. They'll bog down and then you can hit them with your reserves. Set your Velites to 'Fire at Will' on Guard formation in front of your lines.

The key is slowing them down first. Once their charge is exhausted, you can turn off Guard mode and have your skirmishers attack.