I’m also Illinois zone 5b! I would say start out with a few things you are certain will thrive (e.g stuff you see growing all around your area), especially plants from neighbors if they’re the sharing sort. That way you have some successes even if more adventurous experiments fail.
I have hostas, forsythia, black raspberries, mulberries, goldenrod and ozark blue star that were gifts from neighbors or just flat out volunteers that increase every year such that I have split them up to share. I’ve also bought currants, pawpaws, grape vine, and cherry, fig, and plum
trees. All but those last two have done very well.
This year I am excited for harvesting some hopniss (groundnut/apios) that I planted last year. I am also growing a garden of
native crops including corn beans and squash from the Miami and Potawatomi people on whose
land Chicago was built.