What makes basic chemical actions eventually a sexually multi-cellular organism ?
Sexual reproduction increases variation, which results in faster divergence (when balanced against Natural Selection, which it always is).
I can see evolution from there on, even though there are gaps, but the initial push (for want of a better word) that gets it through that stage I just find extraordinarily improbable.
But to be fair, your personal feelings of improbability, can't really be called "gaps" in evolutionary theory. That's just your gut telling you that you don't understand all the stages yet. And skepticism is a healthy thing for science, but it isn't a "gap".