If the goal were purely traffic as you state I would target the emerging markets and trade my premium traffic for these other nations in order to continually multiply. I'm sure you will find no shortage of takers. You could become huge and dominate those markets in a very short time. But there won't be much profit there unless things change. In which case you would be filthy rich. It might not be a bad idea actually!
For what I bet you really meant (build traffic and eventually profit) I'm not sure. The problem is adult is dying for most and it's very volatile. Cams are the safest right now but being an affiliate is the furthest thing from safe. Dating is better than most paysites but that is also in the decline. I'd go with casual dating first before adult dating. The market is better and the opportunities are greater.
I would invest my time in coming up with a great idea and then implement it. Something radically different than what the other guys are doing. That's the only way to get ahead now but you're still hoping that the road continues on for a while as opposed to hitting a dead end where the profit margins continually decline (the story of porn atm) even if you have some success.