The Tampanensis Truffle was the first to be discovered and cultivated. It is also called the Philosophers Stone, due to its rather insightful and reflective effects. 

For most people, 5 to 9 grams have a medium effect, while 15 grams can lead to a strong high.
First effects are likely to be felt after around 15 to 45 minutes and can last somewhere between 4 to 6 hours.
You can eat Truffles or use them as a tea (let it simmer for 20 minutes, don't let the water boil).

BE AWARE that these amounts are averages and can vary from person to person. Always start with a low dose.