I'd say, buy 1/4th, it's more cost efficient to buy in bulk.
Then eat 2 grams to start, because you don't know how sensitive you are and you won't be as crazy out of it. That way you have the option to do more later, or if you don't like it, then you can sell the rest.
Make a 6 hour playlist in advanced so you can have music to listen to without having to choose your music while you're tripping.
Nature's always good.
Set and setting are the most important things.
Check out this site:
http://www.shroomery.org/
There's a ton of good info on it.