Want to start Magento 2 but I am totally lost

I have multiple clients on magneto 1 asking me to upgrade them to the next version . My answer so far is: no! Wait few months. The switch is painful and most of the extensions are not Magento 2 ready. I have also new clients coming and wanting a site on Magento 2, unfortunately many bugs in this version and very little extensions and themes available for M2 make me delaying those developments and simply choosing the older M1 even for new projects. I would love to hear how other web agencies are dealing with it.

The documentation is definitely incomplete but improving every few weeks. If you just need a basic overview http://docs.magento.com/m2/ce/user_guide/getting-started/int... looks good. If you want to do development, keep in mind that the framework was built to be plugin based. If you need new functionality you're building custom modules. If you want to change the appearance, you're working on themes. For debugging you may want to take a look at Z-Ray, a profiling tool built by the magento team.