Don't overthink the amount of rides you will get on. Book your three early in the day and then even high priority rides will possibly pop up for additional FP during the day. We were even able to get Slinky Dog for 3 on one day and Mine Train for 6 on another last week. Between FP, do attractions with low wait times. Even during the busiest times, there will be attractions with 20-25 minute waits. I like using them as fillers.