There is really no 'Embedded Linux'. Using Linux on embedded systems (a very vague term in itself) is embedded Linux. Running Linux on a standard desktop or server (probably without a GUI) is as close to an embedded Linux environment as you will need for the purpose of training.
Using Linux in the embedded systems arena usually implies a knowledge of software development, especially hardware-specific aspects such as creating, installing and applying drivers and kernels. This often includes the use of a cross development toolchain, and an understanding of the infrastructure used to put object code into place on target systems. Embedded systems are frequently not equipped with resources satisfactory for native development, so cross development on bigger systems with more resources (disk, CPU & memory, primarily) is the norm. Usually, embedded systems work involves creation of target systems, but done using a separate and distinct development infrastructure. There is much to understand about this distinction.
Get a host (maybe even virtual host) on which to run a major Linux distro (I like Debian for software development). Acquaint yourself with the native development toolchain (compiler(s), linker, libraries, etc.) Practice building kernels and installing kernels. Learn what all of the scripts and configuration files that run from boot-up are for and start dissecting it to remove all of the stuff that is only used in a desktop or server environment. See how small your system can get. Look at some examples of small Linux distros such as Microcore Linux
Doing the above will lead to a plethora of detailed questions and experience. If you are doing all of this on a full-time basis, expect to spend several months at least, before you start to become productive.