i also agree, it would be much better for you to get a part time job and concentrate on your studies. If you're serious about entrepreneuship, you can always do a masters in business after you finish, and then set off with the right skills and a great product ready to make it work.
As for making money from a blog, i very much doubt it will be worth the time you'll put into it. As you've seen with AJATT, Khatz obviously couldn't make money from having advertising on his blog, that's why he's selling other stuff now. I also put ads on my blog when i first started, because i had wondered why it wasn't possible for Fabrice to do that with this site in the past. Well, i found out... i made $3 from around 5000 views. And ALL of that $3 came from people clicking the ads when people mentioned them in the thread here, out of kindness

Japanese language learners just aren't the right market for that kind of thing. Perhaps if you made a blog about something entirely boring and business oriented, you could make a little money. Otherwise, it's not so likely.
Similarly, with Forex and stuff like that, i highly doubt that it's going to be worth the time you invest in it. Small time trading has been around for a few years now... and the more people that participate in it, and easier the knowledge of how to win at it is to come by, the smaller edge you will have. It is also very risky. Don't believe success stories easily, there's many reasons people would want to say they're doing great, even if they're not.
Please, take it from me. I got into poker when i was at university, and learned the hard way. At first, it looks glamourous, and when you get a few big scores in, it feels great! And you see your friends winning $1000's or $10,000's of dollars, and you want to learn more, of course, and get better.
The reality, however, is very different. Yes, it is entirely possible to make money at poker (and probably Forex too), once you learn enough. But once you look more closely at win rates, return on investment, and so forth, and calculate the hours you've played, you find that you're actually making around minimum wage. If you want to make more than minimum wage, you have to either do sick amounts of work, or you have to take massive swings playing with a lower edge in higher buyin games (which you consequently play less of). I expect Forex is either going to be the same, or will be in the nearish future (i.e. by the time you learn, it already won't be worth it).
There's no free lunch. Work hard at college, work hard at your part time job, and you'll do good in the future, i'm sure.