I'd choose whatever nuts/seeds first, coat them with olive oil (just drizzle over the nuts while on a baking sheet), then sprinkle with cayanne pepper/paprika/red chili flakes to your spicy-ness threshold, then add a little bit of salt (maybe a touch of garlic powder as well). Bake at a lower temperature, say 300-325, for a while until the nuts are dry. Stir them around every so often, maybe every 20 minutes. I think it might take 45 minutes to an hour at 300, you'll just have to see what works.
Sounds yummy though, I don't usually do a spicy trail mix!