Definitely by doing. No question about it. Get your hands dirty. The problem is that the best growth hacking tricks are kept to ourselves. We don't go to these facebook groups or forums and share the greatest and most effective methods we've learned after painstaking trial and error unless we're hanging our hat as a growth hacker. I really don't care for conferences and curriculums.
Here is the best way to learn in my opinion: create a project and actually try to make it successful. Make some gag gift, some drop-ship product, or a hand crafted item that can scale. Then try to blow it up. Create a landing page, put a store together (super cheap and easy with Shopify) and then go! Try all the techniques possible to bring customers: Facebook Ads, SEO, data scraping, email marketing, etc.
You will learn a ton by trying to make things work. No curriculum will make you a great growth hacker or really move the needle much at all. It wont stick unless you can immediately apply and practice. Plus, the cutting edge stuff is not taught in curriculums.
Best of luck!