question about formula for 9 month old

new to the world of formula. I saved one of the sample cans I got from Enfamil while I was still pregnant and we've had to start supplementing. it's the gentle ease kind and so far she seems to tolerate it okay as long as it's 50/50 with breast milk. I'm not able to keep up with her anymore though. we got a few samples in the mail of the toddler transition formula and now I'm confused. is the gentle ease okay for an older baby (9 months)? or do I need to make the switch to the toddler transition formula? the sample can isn't going to last long at the rate we're going so I'm just wondering what we should buy when we run out of what we have.