In general, you'd purchase the individual onboarding package for the Hub you want to get onboarded on.
If you only want to focus on one Hub, there is no need to purchase onboarding for all. You can always add that later should you want to.
We also have a combination package for Sales & Marketing Hub, which is recommended if this is where you want to focus.
On top of this, you have the option to add the technical implementation add-on (not impacted on the number of Hubs purchased) and CRM migration service.
If you have a complex setup and needs, a custom onboarding package is most likely the best fit for you.