My advise for you would be to create your own training projects. You know better than anyone what things you are weak in, and what your strengths are. In my case I created a machine to make widgets. Early on I added an automatic oilier to the machine so I could learn different ways to cycle things on and off based on machine run time. This taught me timers, triggers, compare, and move instruction. Then I made the oilier adjustable so the timing can be adjusted based on conditions. As I learned more, the machine has gotten more complex. Each addition to the machine was purposely designed to force me to learn how to do something new, or improve in an area I'm weak in. My widget maker now runs at a variable speed based on how fast the widget packer running. This brought me into the world of analog input and output. There is an option for adding caps to the widgets based on customer needs, and the machine can track individual widgets as they move down the line. This addition required me to learn how to use bit shift instruction. It also has a combination of Ethernet/IP and DeviceNet communications. I knew nothing about D-Net when I started, but now I can add, configure, or create from scratch a working DeviceNet network. The next planned expansion of my machine will use servos and AOI's because I need to know more about both .
The point of all of this is simple. You are the best person to decide what you need to improve on and when it was the right time to work on it. The D-Net option on my machine came along when I started a new job and found out that 80% of the machines here use DeviceNet, and I didn't really know squat about it. That was a real good clue that I'd better get to learning what this D-Net animal is all about. When you build your own widget maker, make it a challenge to yourself. Include things you know something about, but not enough, and somethings you know nothing about. My machine has been under development for almost 6 years and will continue to expand,and grow more complex for the rest of my working years. Following this path has helped me a lot, and I think it could help you too.
Bubba.