I have complete sets of Topps baseball cards from 76 -79. Got them the hard way by buying packs at the store and trading. Of course there was very few if any rookies worth anything in those years. Even if there were, I abused the cards too much to be worth much of anything to anyone but me.
I collected thru the 70's and 80's the same way. Then in 1992 I sold them all and put a down payment on my house.
I would go to the ben franklin store and buy them for 20, then 25 then 35 cents a pack