The God of the Bible never ordered or suggested that gentiles were to keep Jewish feasts. Those were given to Israel as a sign .
Judaizing Gentiles was rebuked in the 1st church council
They are not Jewish feasts, they are God's feasts:
Lev 23:4 These [are] the feasts of the LORD, [even] holy convocations, which ye shall proclaim in their seasons.
And since God tells us they're his feasts, and Christ kept them as an example, then there's no doubt that the first Christians honored God by observing his feasts.