Ideally indica's. Grab a pure indica or any indica dominate hybrid. Like Sensi Star, Hash plant, Pure power plant, C-99, Afghani, top44, aurora indica... and so on. Oh these all have the shortest flowering times too.
You could also do AF dwarfs easy ryder, poison dwarf etc but all have ruderalis in them and are not clonable. Only way to keep going is to germinate a plant for seeds