My little one (3.6#) is a very picky eater also! I tried all kinds of dog foods. I finally started giving her boiled chicken breast in the mornings. I boil up a couple at a time, cut it up into bite size pieces, bag it up and freeze the rest. For a little variety I've found she will eat ground turkey as well. She is allergic to beef so this seems to work well. She can't wait for her breakfast every morning. I still want her to eat some dog food so someone on here suggested sprinkling a bit of parmesan cheese on it. I often will do this in the evenings. She will eat a little bit that way. She picks out the kibbles that she likes, and I find the rest of them strewn throughout the house!
Good luck with finding something that works for your little one. I know how frustrating this is!