My flock is about that size, 13 ar present but will be about 25 once the lambs all arrive. I expect you have see Wombles excellent outdoor arrangement?
I bought a second hand run and have used hurdles to create a collecting pen and a couple of holding pens. I do use it occasionally but have to say with a dozen sheep it is actually quite tricky getting the pen size right such that they don't just wander around rather than go through the race. I positioned it by the gate between two fields, but even after thinking hard where to,put it I often find it easier to take a few hurdles to the field they are in and work with them in the field.
As to the big equipment, I keep mine in the barn and use it after they are in for lambing then again later in the summer out in the field. As it is very dry here it is ok to leave out through the summer
So to summarise, although I love the look of the sheep run with under 20 sheep I haven't found it as useful as I thought I would and a shepherd crook is just as effective for sorting the sheep when I need to split them up.