I smoke weed and always have, off and on. I'm not a stoner but I love to smoke on moderation. It eases pain and helps me get into a meditative state where I usually can see things I am missing about myself or my life from my "normal" view.
To answer your question, you don't need very much to get high if you rarely or never smoke. 1-2 hits maybe. And no, you won't do anything crazy. It's not like "reefer madness". You'll feel good, relaxed, deep thoughts, happy, creative, etc.