Trench size for 100mm Agi pipe

[Aabey]

Hello All can you please help me, in my garden water get staged during rainy season. I want install some agi pipe for 25 metres, please advice me on following 

1 what is the size of the trench I need to make for 100mm agi pipe.

2. What is the best brand of agi pipe I need and how many meters.

3 How much gravel I need for to and bottom.

4 Do I need plastic under lay for top and bottom of the agi pipe

Plus any other information I need to know.

Thanks in advance