There are so many niches available in the market where publishers have not yet tapped. Internet Call is definitely a good niche. Go to dmoz.org to know different niche (Not the right place but no harm in trying).
Arbitrage is very risky. You can earn from it for months, but surely Google can see you and sadly, will smack you out.
Very true! Arbitrage is not a good idea. But follow what google says and go google way. Google don't stop publisher to come up with their niche. So go Google way!
niche's are really very difficult to identify unless you are really on a hunt for one with your research and analytic tool. But again coming back to the topic of "arbitrage", it is not the right method of making money using adwords traffic to click on Adsense Ads.
I agree with spending that money on organic traffic than adwords. Google can slap you with high CPC anytime.
Article writing can be achieved more easily by allowing other people to post on your site and include their links. You can add your own links to 'their' article pages. It's a relatively passive income source. Adsense income is pretty good, can be nothing some days though for some reason. At least I expect to pay my monthly subscription fees with adsense and increased levels of articles. Adwords seems to drain my budget, otherwise I'd be onto it ! A good source for adwords knowledge is kill your day job. Does anyone know if its an 'oldy' seems to work ok still.
I just remembered that I have around 50 google coupons with 30 Euro each. Well good buyer for it let me know.. Sorry I am not selling but just came to my mind. People don't think to learn adwords in a day! It is not that easy as you think. But yes unless you want to make a living of adwords.. don't try!