How can I build my network?

Same situation here.
My suggestion and way is:

1. LinkedIn posts, comments, connections and engagement (good for introverts, also well documented and less chaotic)
2. Carefully keep in touch (virtual at least) with potential and talented seniors, juniors and classmates (college). They might be very influential in future and they might be all the network you will ever need in future. (That's very common and true for IITs, IIMs batches etc.)
3. Choose the man within your network that seems like a good network to have (CXOs, Investors or persons with good network) and try best to network them offline casually.

Best of luck (to us)