I look at it a different way. Instead of what kind of cards I should get, I ask myself:
1. Where do I want to go?
2. What airlines fly to that country? Which ones do I actually want to fly?
3. Is it easy to find award tickets for that trip? For example: I've read that it's hard to find premium seat on Qantas from U.S. to Australia, so accumulating AAdvantage wouldn't work unless I want to fly to Australia via Asia.

Once I answer all of these questions, then I have a goal. Say my goal is to do business class RT to Australia. I can either accumulate 160,000 Delta Skymiles, or 188,000 Flying Club Virgin Atlantic. Now I build my strategy based on this goal. I start looking at which card can convert points to Skymiles or Flying Club. Then I'll try to apply for whichever cards that will get me closer to this goal.