I'd say an 8th is enough most of the time. The last time I could get any shrooms around here my friends I ate a little over 5g each and that was just crazy, but it also showed me how much the same amount of the same batch of shrooms can vary from person to person. My ex-girlfriend ate them and just sat and stared, she couldn't understand us and couldn't really talk at all. My friend just puked and was just really anxious the whole time while he was tripping. I just enjoyed it all until I couldn't hold back from hearing my friend puke and puked, but even then it wasn't bad. Pretty much if you're in the right mindset you'll be fine.