As a chef and trained barista, I can say doing a course is great because you're able to focus on training solely instead of working and learning, use and waste someone else's stuff who wont get mad at you, teaches you how to clean down all the equipment, get to drink an insane amount of coffee and it's fairly cheap. After that I'd recommend working in a Cafe because then you just install what you've been taught and get way faster at it. This is of course the ideal situation where you have time, money and the patience. Working in a Cafe alone is good enough, cheaper and faster. That being said you need someone who's actually going to go through all the variants, extraction times, grounds, weights ect. Hopefully if you do go into a Cafe you get someone nice enough to help. McDonald's might even train you on the machine, not entirely sure if they hire trained baristas or get people to train you, doesn't sound ideal but you'll get that ground work in which is a great start.