Real talk - and this probably goes against a lot of what is taught on these boards - but banging a LOT of chicks is highly over-rated.
I went though my entire college experience banging ZERO chicks. Since I've graduated, I've banged a LOT of chicks. Given the two options, keeping your numbers low and only banging girls you're trying to get with is preferable. Also, in looking back on the chicks I wanted to bang while I was in college, I don't feel bad about not banging them now because I see what they've become, and most of them have no direction, have gotten uglier (and I'm talking about girls that used to be dime pieces in college), and have decreased in lay value.
Also, every time you bang a girl and then leave her, you're actually adding to your own personal baggage. It may not be a thing that seems important NOW, but 10 years from now when you meet up with that special someone and want to commit, you'll find yourself having certain problems arise. For one, you'll be so used to banging and leaving that, initially, you'll feel yourself being ready to "next" your girlfriend - not because she did anything wrong, but because you're just so used to only having short flings.
You'll also find yourself trying to form a sexual relationship with this person based on previous encounters you've had with other girls, which may or may not match up with what works for her. For example: you may have been with 10 girls who all got off whenever you kissed their necks. Now that you're with your "true love," you find she doesn't get aroused by neck kisses. So, all that "experience" you gained with the first 10 still doesn't mean you automatically know all the things you need to do to get #11 off.
Anyway... to answer your questions directly:
1. NO, it's not just a number's game. The only one who should care about your scoreboard is YOU, no one else. Your friends are morons - there are things called STDs out there, and young women are oftentimes the WORST at protecting themselves from it. I can't be too much of a hypocrite by saying "don't bang a lot of chicks," but I'm telling you, it's really not all it's cracked up to be. You may feel you're at a point in your life where you just want a bunch of lays, but if you meet just ONE girl who's giving it to you regularly, that's all you really need. At some point, p*ssy is just p*ssy, and even newer versions of it eventually start to feel the same as the last one...
2. Ever met or heard about those people who are celebrating their 50th or 60th anniversaries? They started dating and/or got married around your age. Don't ever think you can't find "the one" while at university. Yes, the odds of it happening are lower, but it's also a waste of time to just be banging random chicks - again, all that stuff takes an emotional and psychological toll on a person, and it WILL come back to affect your later relationships.
3. Relationships are only a waste of time if you (a) don't learn from them or (b) are using one as a means to detour from your goals in life. Again, your friends are morons. The only thing you'll regret later in life is not taking a chance at being in a serious relationship with someone you thought would work out for you. You will NOT - I repeat, NOT - regret not banging that slvtty chick that everyone had a shot at, or missing out on a random hook-up. TRUST me, when you end up with a girl who truly loves and cares for you, you'll actually feel BAD at times for having all those experiences outside of her.
4. Lastly, being in a relationship isn't just about being happy. Happiness is over-rated at times. Not to say you shouldn't be happy in a relationship, but it's about much more than that. It's about being there for the other person; being able to work through problems instead of just walking away; and doing things that benefit the other person, even if it's not something you always want to do. These are things you have to be mature enough to do on a regular basis in order to have a functioning relationship. If you're only at a point in your life where you want to be selfish and put your own needs before someone else, then no, you're not ready for a relationship and should (a) stick to either being alone and learning those things or (b) banging random chicks. I wasn't ready for a relationship a few years ago, so I chose option b: banging random chicks. Looking back, it wasn't the best decision I could have made, but I wanted to get my rocks off so that's what I did. I still have those urges now despite being in a relationship, which, as I stated earlier, is one of the affects of consistently being in the practice of banging different chicks.
Anyway, I hope some of this has helped you a bit in figuring out how you want to proceed in your dating life. Best of luck to ya!