A good floutist needs good posture, lung/breath control, and dexterity. Complete control of the mouth is necessary to create proper sound. Flexibility with fingers and ability to stretch the hand; the more flexible obviously the better.
Baritones players require strong lungs and good posture. Don't worry too much about lung strength if you are just now choosing because you will develop them as you play more.
If you practice a lot, it's really not that hard to excel in flute playing. You just need to keep practicing. If you don't practice then you will never get better. I have been playing flute for...