You just contradicted your own statement. If the OT "lays the foundation" then it is part of the gospel. The implication being the gospel has no OT foundation, no foundation at all, and the NT is an entirely new and radically different revelation begetting a radically different religion that has absolutely nothing to do with the OT.
Scripture proves otherwise. Nearly everything Jesus taught can be found in the OT.
That is not entirely correct because the word
euangalion means good news of a specific kind, not just any
kalon akoe. A euangalion was good news of a great victory won by a great warrior or king. See
HERE. There are more than two dozen references to good news in the OT and most of them can be understood typologically as the gospel foreshadowed. There is no greater victory than that in which sin and the grave are defeated and
that is decidedly found in the OT.
Appeal to ridicule noted.