I don't have all of Clancy's books, but I do have the ones about Jack Ryan. I would begin with "The Hunt for Red October", then
"Patriot Games", "Clear and Present Danger", "The Sum of All Fears", "Debt of Honor","Executive Orders" and "The Bear and the Dragon". Two other books, "Rainbow Six" and "The Cardinal of the Kremlin" give the histories of characters found the the Ryan books, and could be read before, during or after. Clancy has written other books, but I was only interested in Jack Ryan, so I can't comment about them.
Hope this helps. You can probably get a good deal on them at Amazon used books. They seemed quite low priced the last time I checked.
Carolyn