If all you want is a preview of a mushroom trip, you are looking for a light but active dose. Psychonaut Wiki says a light dose of psilocybin is around .5mg.
Dried mushrooms are commonly accepted to be 1/10th of their fresh/wet weight. Dried Liberty Caps are on average 1% psilocybin per Wikipedia - fresh Liberty Caps will be .1% psilocybin by weight.
So then x grams of fresh Liberty caps times .1% psilocybin should equal .005 grams of psilocybin
5g of fresh caps
Or just use this
https://www.shroomery.org/6257/Magic-Mushroom-Dosage-Calculator>>2473308ghetto as fuck