hey,
Read books on Embedded Systems (e.g - Embedded systems by Rajkamal)
Its expected that you know C programming before going for embedded systems
have read and know atleast one microcontroller and one processor like 8051 and 8085 (currently ARM cores and PIC and arduino are used)
have read and worked on linux , a little bit
Hiii,
To learn embedded systems you should know about c programming/assembly,digital electronics basics,basics of networks.I would recommend you to buy Tiva C launchpad and join a free MOOC course hosted on edx.org by Utexas.Understanding concepts is important and not the board that you are working.You may find A book written by Prof. Jonathan Valvano very useful
Are you already familiar with digital electronics or some kind of programming.
If you come from a programming background then the Raspberry Pi, is a great way to transition from PC programming into the embedded world.
You can be up and running for about USD30-40 and start learning how to control I/O pins with loads of help on the internet.