I like this guys idea of watering system from a rain barrel. It could be better if his garden was closer to the water supply. His water has to travel quite some distance through the pipes. I understand how some things aren't possible though and you work with what you have.
I really like his 'manifold' set up better than a soaker hose. Also his hint on how and where to place the holes. And also his spigot advice.
See the "T" pipe coming from his downspout at about 1 min. into the video? I think I'd try to put a "+" pipe on there. That way you could cap the bottom for normal use when filling the barrels and then uncap it and put on a regular downspout when the barrels are full or for winter use. I'm not that handy but in my mind that could be an option.
I also noticed his barrels are up on two layers of cement blocks with pavers for stability. I mentioned that in another post. I saw that in another video and liked it. It looks nice too. It's around 30 sec. into the video.
https://www.youtube.com/watch?v=6-emq0cxhtU