My advice is to run one or two additional, level-appropriate Starfinder Society adventures after you finish 'Into the Unknown'. My main group played 'Yesteryear's Truth' after that one, and then 'Star Sugar Heartlove'. The three adventures gave you a good look at different types of content, and you can decide at that point if you want to continue using prepared content or branch off into a home-brewed universe.
I also recommend the Aeon Throne adventure path. It's short (3 books), so you aren't committing to a long slog when you start it, and the stories and encounters are really interesting and fun to play. The only downside is that when you finish the AP, you will have players with characters they love with Signal of Screams as the only level-appropriate content available from Paizo.
If you're up for a 6-book adventure path, all of Dawn of Flames and Attack of the Swarm is available, so you've got some good options there.
To answer your question about the home-brew: creating a game environment that's compelling and cohesive is a massive amount of work, and the amount of preparation you need to devote to that process is hard to quantify. Decide if content creation is how you want to spend your time, because your party can't play unless you're ready to GM for them, and it's far quicker to bring a published adventure to the table than it is to write your own.
Having said that, you can test the waters by creating your own encounters that you insert into the prepared content. Draw up a wrecked spaceship for them to salvage. Insert a space goblin mugger into an alleyway of Absalom Station. The possibilities are endless.
Enjoy!