bullsh*t, fresh are more potent, simply because drying is often done too quickly and potency is lost and also fresh are absorbed by the stomach better.
with psilocybe mexicana (philosophers stone) depending on how you wanna trip depends how much u should take, here is my rough guide:
-5grams buzzy and things are very funny,
-10 grams more of a trip, mild hallucination, strong philosophising about the meaning of life etc (and yes- on a higher dose you'll probably think you've discovered it!)
-15 grams same as above but stronger
For more effect wash your mouth thoroughly with an alchohol based mouthwash which cleans your mouth and lets the tissues become more absorbant, then chew it for as long as you can bear (10 mins if possible) and you'll get a much quicker and stronger effect.
Good luck and have fun!!!
Jonny