If you're going to be a churner start with the easily-churnable ones and only when you have a churn wait period get the ones that are usually once-only bonuses.

Alaska is an easy churn every 90 days, as is Hawaiin, US every 6 months, American every 18 months, etc. Chase and AmEx sometimes are very long "churns", if at all.

Also get cards a.s.a.p. that are dying- AirTran and US.