I identify as genderfluid, so perhaps I can provide a few tips. About binders: so long as you are using a proper material, it shouldn't harm your breasts. There are several brands of undershirts that are designed specifically for binding breasts (you can find some online that are relatively cheap). If the idea of binders scares you though, there are other methods to make them appear smaller. For example, using two small sports bras: one facing the right way, one on top facing backwards. It may feel a bit strange at first, but it does work and the discomfort should go away fairly quickly.
Don't feel like there is a 'right' and 'wrong' way of being genderfluid. You create your own identity, so you decide how to interpret it. I have weeks where I feel like wearing only skirts and blouses, and then I have weeks of camo pants and rock t-shirts. It may be confusing to some people (including to myself), but I do what makes me happy. Take your time figuring yourself out! It's okay if it takes some time; just go at whatever pace you are comfortable with.
Best of luck!