It is hard to improve the CPC on non-english site. Suggest use adwords tool to find the high pay keyword on your languages
I say beat it to the punch and get your well deserved virgins. /kiddin Regarding CPC - I'd assume that forex, insurance and law niches would pay well in any language. Generally, the more competitive and conversion-oriented the niche, the higher the CPC.
Change your site's language to English. It's easier for Adsense crawler to determine which ads are suitable for your site.
You are wrong Adsense in Arabic has been available for quite a while, and Adsense for Search in Arabic has been available for almost two years. Both are mature and well developed implementations.