Starting points for beginners

I’m an old guy looking to start a second career ('cause i don’t want to retire) in the Web3 space. Generally, besides the basics of studying and research, what critical points of development must be accomplished to become an effective developer?

Also, what are the necessary milestones that should be considered for building a development team behind a project?

Additionally, how important is marketing and what avenues work best in today’s web3 environment?