Ultimately, if you want to go beyond the back bridge, you can work towards the stand to stand bridge. I suggest working on the gecko bridge, which is one arm one leg. Now, there’s no time limit on bridging, but, anecdotally, I was able to do a gecko bridge with opposing limbs for 30 seconds per pair during my warm up routine before I even tried the stand to stand bridge.
You can do the exercises in whichever order you find most comfortable, or you can do alternating sets.