What leads you to think this?
One major is enough; many companies look at GPA and a low GPA can rule you out but no second major won't. The GPA/more classes pareto curve is also usually more favorable towards one major. But if it's a very small commitment for OP my advice doesn't stand.
What kind of effort?
Talk to people, be friendly, stay in touch, initiate social activities, be a good friend.
I think you're missing,
my interests don't intersect with most of my peers' (see the partying / drinking / buying expensive food stuff above). I'd rather spend time with people who are doing interesting things and who I can relate more with (is this bad?), but I'm having trouble finding such people on my campus.
All your suggestion are good, but it's not worthwhile to put lots of energy in building friendships with people that you don't like.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
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