You have to do squats to gain size and strength. The brutality of the exersize will stimulate your central nervous system to recruit more muscle.

A very simple push/ pull would probably do you well.

Mon /Push

Squat
Bench
Pushpress (over the head press)

Thurs/ pull

deadlift
Bent over Row
pullup

Possibly throw in some weighted ab exersise at the end, but it's not really necessary because the squats and deadlifts stimulate your core.