Go to class. Do not skip classes unless you have no choice (so sick you can't get out of bed, surgery, funeral...)
I followed this rule for my first 2 out of 5 years of engineering school, and everything was good. Classes were hard, but the work was always manageable if I put enough time in it.
Then, I started slacking off, because everybody said that after the 2 first year, it's basically easy peasy. When it's not. I started by missing a single lecture. Then another one. Then I was a bit afraid of coming back and not understanding, so It started to create a vicious circle.
I was like "Lectures are so slow, I know that stuff!", "I'm sure I can just read the material online and understand all of it in half the time!", "If I don't go, I can sleep till 9!".
Besides, waking up late only lead me to go to bed late, and made it even harder to go to class in the morning the next day. It's really bad.
Even if some lectures are a bit slow ; slow and steady wins the race. Having time to learn something properly and ask questions is a privilege you should never throw out the window, even for a couple hours of sleep.
Even if the stuff looks easy/useless at the beginning, it doesn't mean that it will stay that way. Usually teachers make the beginning of their lectures easy so everyone can understand, no matter how much previous knowledge they have. It usually get harder really quick, and if you've missed important lectures, it might take you 5 times longer to realize what you misunderstood/didn't know, and try to understand it (asking a friend, etc...)
The material won't be online all the time, so you actually have to be there to get it (depends how you school works, if they print the slides for you, give you specific textbooks...).
I've made the mistake of skipping almost all of the lectures in a specific subject, I didn't have any material, and even if it started easy, it ended up being one of the toughest subject all semester. my lab (as in computer lab) partner had skipped all the classes too, so when the time came for the project, we were both completely lost. We failed the project and the finals. We had to pass the exam again in September. My partner had received help from friends so he passed. I ended up failing again. I had to pass it a third time and failed it again. I did a project to make up for it, but I still don't know if I will pass or not. Keep in mind that I had all of the other classes, and the rest of my scholarship and activities to do while I had to prepare on my own, without any teacher to ask questions to, and try to pass it again. Even when I failed they wouldn't tell me what I had done wrong, so I had to guess what I didn't understand.
Overall, I've been very stupid for skipping the classes, and I've handled the consequences quite badly, so that lead up to 2 years of stress, and more weight on my shoulders, that my friends didn't have to deal with. It was always in the back of my mind, that I needed to pass the test again, that I didn't even understand what I didn't understand, and had so much to keep up with at the same time. It was really frustrating.
TL;DR: Go to class. It's the easy way. Skipping class is not the easy way. It will lead you to have to work more, and might put you in a world of troubles. Go to class, sit down, take notes.