I like to use pineapple and hog, I have used green crack and grape ape before, but if your looking for a higher yield I would go with the pineapple and grape ape
You may want to consider some of the autoflowering strains. For expample Auto AK47 from Lowlife seeeds. Has a reputation of high yield and potency (for this type of plant).
However, being an autoflower, you cant really clone it. So either you breed for seed, or buy seed for every batch. Hope this helps.