Another one now on its way to me. Probably a 50s/60s era style? Donegal Tweed.
Warning: Spoiler! (Click to show)
I read it to a class of second graders. The other teachers poo-poohed the idea saying that it was 'way over their heads. Hah! The little ones sat on the rug entranced, mouths opened and examined each picture in detail. Great story. Not only the original but the Disney cartoon and the BBC claymation version with Ian Carmichael. They're all wonderful.
The short answer is, use a pattern that you like! Herringbone and houndstooth are pretty uncontroversial patterns and would make a good first suit. Honking loud checks, like the Harris Tweed Tartans, are perhaps best left for when you feel more adventurous.
Some family-owned mills which make excellent, very reasonably priced tweeds without merchants' markups can be viewed below. I have garments made from each of their tweeds and I am very happy with them.
Islay Woollen Mill, Scotland http://www.islaywoollenmill.co.uk/
Trefriw Woollen Mill, Wales http://www.t-w-m.co.uk/
Molloy and Sons, Donegal, Ireland http://molloyandsons.com/
Isle of Harris, Harris Tweed, Scotland http://www.harristweedisleofharris.co.uk/index.php/aboutus