Schematic and PCB Design From Scratch
If circuit DESIGN is what you are asking for (????) then you should know that a great many commercial (and open-source) products are based significantly (or completely) on the "reference design" provided by the chip designer/manufacturer.  And, of course many (most?) of the microcontrollers out there are Open-Source which means that you can copy them completely (or partially) and use them as your own.  And even circuits which are proprietary or protected in some way can be excellent sources of inspiration and learning WHAT they did, HOW they did it, and perhaps most importantly gain insights into WHY they made the design decisions. 

There are several YouTube channels which feature "tear-down" videos where the host takes apart something and does on-camera analysis of the design and manufacture with likely-accurate specualation about the trade-off decisions that went into the design.  One very popular channel is http://www.eevblog.com/ which also features an online forum where issues brought up in the videos are discussed by knowledgable people. 

Your initial question is quite ambiguous whether you are asking for help with:


Circuit design
Schematic drawing
Circuit board layout


Or perhaps some combination.  It would be very helpful to clarify your question.