For the HOUSE OF MYSTERY and HOUSE OF SECRETS, they have Bronze Age Omnibus editions.

The first volume of HOUSE OF MYSTERY collects issues 174-200.
And a 2nd volume I saw collects H O M issues 201-226.
https://www.mycomicshop.com/search?TID=47930099

The range of outstanding artists doing work in these issues, particularly when Adams and Wrightson, Kaluta, Redondo, Nino, Toth and others began, you really can't go wrong.

I have no interest in the black and white SHOWCASE reprints of these issues, but those are available too.
https://www.mycomicshop.com/search?TID=754721