I pursed with glopol this year without having ½ previously done. So I wouldn't say it's that hard, easy to pick up on.
This is because politics is always changing and renewing itself in response to global issues.
The biggest challenge is keeping up to date with case examples and the news (half the time done by your teacher - dependent on your teacher haha). Of course the memorisation of key statistics and global actors are essential when answering SAC questions and most important, the exam. Like I said it isn't hard, nor is it easy. You need to be willing, hard working and committed to do well in glopol.
People who enjoy politics, movement etc tend to love the subject. I chose it because I've always found politics interesting and whatnot.
You might want to check the study design to see what you'll end up learning. As for units 3 and 4, the course is designed all around global actors and in which their presence has been effective in response to a varying world, asian pacific powers and national interest, ethical issues, and crisis.
I for one haven't yet finished glopol as a subject yet, but am enjoying it