well university isn't QUITE real life yet, especially if you're gonna be living in dorms.
That said... here are some tips:
-in addition to the ramen and sandwich stuff that has already been mentioned, eggs are awesome too. They're both cheap and versatile-- you can have them scrambled, sunny side up, in an omelet, etc. My diet as a poor college student consists mainly of eggs for breakfast, pb&j for lunch, and ramen for dinner. Sometimes I go out to eat or cook something more elaborate, but that's only when I'm feeling relatively rich
-Independence? Ehhhhhh just relax before the year really starts up, because once you get school work, you're not gonna have much free time. And in what little free time you'll have, you'll probably want to see your friends!
-Friends: just talk to people and eventually you'll make some friends. Roommates are an excellent place to start if they're not douches. Classes and extracurriculars are also good ways to meet people. If you're into parties, you can probably meet some cool people there too.
-What to do if you don't know what to do: surf the internet and eat peanut butter out of the jar with a spoon. Or you could splurge on ice cream... and if you're REALLY lucky, you'll have enough free time/cash to get a Netflix subscription. Alternatively, you could just text your friends and see what they're up to. Interesting things to do also vary by location, so maybe just google "Free stuff to do in [insert name of town here]"
-How to make your room your own: just don't clean it. That way, everyone will KNOW it's your territory and your territory alone. Oh wait you were probably talking about posters and shit.... well, just buy a couple of posters that portray content that is somewhat related to your interests, or that just look cool. And maybe buy some cheap but interesting-looking furniture at Target. Also make sure your sheets and comforter look cool, because your bed is probably going to take up about half the space in your room.
-general discussion on independence: i haven't REALLY experienced it fully yet. In fact, I don't think anyone really has aside from the super-rich. I mean, think about it: no matter what, you're probably going to need to answer to someone. In high school, this someone was your parents (and also your teachers to some extent). Now, it's probably still gonna be your parents to an extent if they're helping to fund your education in anyway, and also your professors (well, they don't care what you do in your personal life as long as you know your shit) and the University bureaucracy (who actually do kind of give a shit if you deal drugs from your dorm room or something like that) and your RA (basically another parent packaged in college student form unless your RA is REALLY chill). I mean, obviously the environment won't be as restrictive as it was back home, but you still have plenty of obligations to fulfill, assuming you actually care about grades and career and all that jazz. I guess the advice I'd give for this is to stay on top of your shit, but also make enough time to RELAX. Make sure to see your friends every once in awhile, and also make sure to have the occasional day where you don't even change out of your pajamas and just watch Netflix or cat videos on Youtube all day (but for the love of god, make sure this day isn't a day when you have classes because classes are fucking IMPORTANT). Oh, and go to class... every class... even if it seems like bullshit. If you don't end up gaining anything useful, it was just an hour of your life, but going to class has a far higher chance of paying off in the long run than spending all your time watching cat videos. And DEFINITELY study. A lot.
OH ALSO caffeine is your best friend. Alcohol may or may not be your second-best friend, but try not to become TOO closely acquainted with it, lest you become an alcoholic... though the occasional fun night out with your friends is awesome. Know your limits, don't get arrested, and for the love of god don't drink alone at all ever.
EDIT: this came out sounding more bitterly sarcastic than I intended it... so take the biting sarcasm with a grain of salt. Uni life is actually really awesome in that it's the best of both worlds: you're on your own for once, but you still have a huge network of people to support you and a TON of new opportunities just waiting to be explored. Just keep an open mind, talk to people, do your school work, and everything will be fine :)