Light gaming? Sure, mac books will be sufficient enough.
I personally hate macbooks and I always laugh when people use mac book and gaming within the same sentence. But we are here to emphasize YOUR personal wants, not what people think of it. Do you like it? That's all that should matter. If you decide to not get the mac book, you can take a look at this. One of the best laptops for gaming under $600:
http/us.acer.com/ac/en/US/content/model/NX.MCTAA.005
If you're using it for school & business oriented activities via spreadsheets, you may want to look for a 1080p laptop. I don't think you'd be too comfortable working with a 720p laptop (like the one I have suggested above). League of Legends isn't a very demanding game at all, so integrated graphics should handle it just fine after some tweaks with the settings. If you want, you could take a look at the Lenovo U530 Touch ultrabooks (lower models; has intel HD4400 integrated graphics); I'm about to buy one of the higher end models with the dedicated graphics card on monday.
IMHO, I'd stay away from used products. When it comes to laptops, I ALWAYS buy brand new so I wouldn't have to worry as much about problems. For desktop parts, I don't mind buying used parts because you can easily swap them out if you have problems. But laptops are basically a system that cannot easily be replaced, so new is what you would want to look at. Again, this is my personal opinion.