The definition of "best" is different for each enterprise. Use the tools provided my Meetup to evaluate the quality of each group. Contact conferences and ask for references.
Great question, that depends on the raise you want to do. Just saying VC networking seems too broad unless you really just want to network to build your network. There is always the old school way of going to crunchbase and looking for companies to see which VC backed them. Then taking the time to reach out for personal meetings or introductions.
It is not in NYC but Disrupt SF 2019 presented by Tech Crunch would be a great place to start. Dates are Oct. 1st-4th, 2019.