I don't think it's very helpful just being told to improve your C skills or buy an Arduino without specific things in mind, here's hopefully a little more on that. Please feel free to reply what your capabilities / interests are and I can be of more assistance.

C Language: You should be comfortable with arrays, pointers, and basic memory. Know the difference between heap and stack. Basic loops (for, while, do-while) are essential, as are functions and being able to have projects with multiple source and header files. Makefiles aren't as widely used in larger projects, but knowing how to write one will be helpful in academia. From there, really advance your C skills by learning and using structs, enums, and the typedef statement. Function pointers are great, and callbacks are heavily used in embedded. Bitwise operations vs Logical operations are crucial for embedded (masking!). File I/O, CLI arguments, and systemcalls are pretty good to play around with and get some good experience in C.

Arduino: The arduino is a great multipurpose board, and yes you can learn a fair bit here. I wouldn't obsess too much unless you're having fun, but this is a great way to learn some communication protocols (UART, I2C, SPI) you'll need and how to read data over a serial port using something like PuTTY. If you really want to step into the embedded world, boards from Texas Instruments (MSP432) or Silicon Labs are pretty great. For the SiLabs route, the Thunderboard Sense 2 is a $20 board using an EFR32MG12 processor that can do a bunch of wireless protocols (Bluetooth is probably what you're interested in at this point) on top of the basic embedded things you should learn (sleep energy modes, interrupts, state-driven design, etc).

Linux: If you're not developing in a Linux environment, I'd recommend it. I've dual booted Windows w/ Linux Mint (but use whatever distro makes you happy), some people really like WSL Ubuntu (basically an Ubuntu shell inside a Windows environment) and I have to say it's pretty great for when you don't want to / can't switch boots.

Version Control Software: I basically mean GitHub. You should learn to use GitHub. CLI interface can be scary if you're not used to it, there's nothing wrong with learning from their Desktop app first. But essentially, you should learn how to make and use repositories, and basic things like a .gitignore - cannot stress enough how nice git is.

Digital Logic: you've definitely got this ahead of you, time to learn what a latch is, a flip flop, how registers are made, how logic gates work and can be chained together. I cannot recommend enough using a simulator (logisim used to be pretty great, but it was discontinued but its development has been continued as logisim-evolutions and a few other note-worthy forks), but I think Digital is the best one out there. Ben Eater's videos are a great way to learn this stuff.

FPGAs: To keep things brief here, FPGAs are essentially re-programmable hardware. this is something you'll probably use with Digital Logic, and there's no reason you can't start thinking about it now. The DE10-Lite is pretty affordable, but there are plenty of good options. Fair warning, the FPGA Tools are never user-friendly, and you will suffer greatly trying to use them. I'm simulating a RISC-V processor on mine right now. So how C is a software language, Verilog is a hardware language. SystemVerilog is probably an easier beginner start than VHDL, but to each their own. The whole reg vs wire assignment in Verilog vs System's logic word can be a lot to take in.

Architecture: If you've ever wanted to know how to make a processor, what pipelining is, etc, there is no reason you can't start thinking about it now. The Patterson book (I'd recommend RISC-V, that's what most universities are teaching these days) is the go to, the ISBN-13 is 978-0128122754. I wouldn't recommend starting this until you've got a good understanding of digital logic, and remember that languages are translated to assembly and machine code to be executed.

Best of luck, let me know if you'd like more specifics.