I guess my question to you would be what are your goals? Do you have a project in mind? Do you have a technology, Analog, RF, MCU, FPGA, embedded design? I tend to learn a new thing better when I have an end goal or project to work towards. Depending on where your starting from, a pi might be a good place to start too. You still have most of the I/O and busses of an Arduino, but you can program everything in python, and you have the resources of a full OS too.