Just do one small line or key bump. And then go from there. You'll know pretty soon if you want more. Plus when most people do coke they don't do it all at once. My coke routine was do a couple lines, go out. Have a drink, do a couple more bumps etc. But one small line or small key bump should be fine too start. Then maybe more 30-60 minutes later if you don't feel overwhelmed. If you're a human being, which I'm pretty sure you are, you're gonna want to do more at some point. Its inevitable. Just make sure you're heart isn't racing outta control before you redose.