Baby food question

My daughter's pediatrician recommends introducing one new food at a time and waiting a few days between new foods so that if she has a reaction I'll know what food is causing it. I'm pretty sure most people do this? But my question is.. I started my daughter on avocado and she liked it and I had her eat it twice a day for 3 days. Then I gave her green beans once and she didn't like it and wouldn't eat it a second time. So then I just started her on bananas but she doesn't like them either and would only eat them a few times over 2 days. So should I just feed her avocado until a few days passes to make sure she doesn't have a reaction to the bananas or start her on something new? If I start her on something new now and she has a reaction maybe I won't know if it's the banana or the new food. I'm just wondering if anyone knows what's recommended when a new food isn't liked and is only eaten a few times