Start your trip as far north as you plan to go. The Pacific coast is much better viewed trwvelong north to south. The ocean is then on your right where most of the turn outs also are.
If your planning the trip this summer, good luck! Most likely you will find reservations in most parks already gone.
In Oregon, you will want to try Ft Stevens state park, Beverley Beach state park, South Beach state park, Salmon Harbor at Winchester Bay, a private park for starters.