For most people, creating an hour in their day for fitness is something that can be tough to do. Even getting in 30 minutes of something is better than 30 minutes of nothing. What I would recommend if you only had time for 30 minutes and you wanted to get in a quality workout; I would focus on starting with a compound movement-meaning involving multiple joints. This would be a variation of the squat or deadlift. I would recommend doing two warm up sets and 3 working sets of 5. A compound movement like the deadlift allows for a higher recruitment of muscle fibers as compared to a bicep curl. We would then lead in to an upper body pulling motion and then an upper body pushing motion, coupling in farmers walks, as well as squats.
We always move from general to specific. Larger muscle groups first followed by small more specific areas. A sample 30 minute workout that I would do if I was trying to be as efficient as possible with my time, would look like this...
1a. 3 sets of 5 Deadlifts-80-85% max
1b. Band pull aparts 3x10
2b. Farmers walks both sides 3x
3a. Push up variation on the floor (feet elevated, close grip, on barbell etc.) 3x
3b. Walking lunges 3x