It seems rather reasonable to assume that there was a historical buddha, and reasonable to assume that teachings repeated consistently throughout the suttas came from him. Basically, the 8 fold path, noble truths, dependent origination, are almost certainly in my mind the teachings of a guy named Gotama from roughly 2500 years ago. And I think the sutta pitaka and the vinaya pitaka are the foremost authorities on what counts as buddha dhamma, with the suttas being more important than the vinaya. Afterall, the vinaya wasn't formulated until the sangha got too big to be full of only good bhikkhus.
"I don't envision a single thing that, when developed & cultivated, leads to such great benefit as the mind. The mind, when developed & cultivated, leads to great benefit."
"I don't envision a single thing that, when undeveloped & uncultivated, brings about such suffering & stress as the mind. The mind, when undeveloped & uncultivated, brings about suffering & stress."