What you buy, and how you arrange it, will depend a little bit on what's important to you.
I like to be able to see my depth all the time -- I probably check my depth gauge every 10 or 15 seconds when I'm not actively looking at something specific or taking a photograph. So I like that information on my wrist, where it's right in front of me, and on my right wrist, so I can watch it as I add or vent gas from my BC.
I clip my pressure gauge off on my left, partially because the HP hose is there, and partly because it doesn't cross the front of my body and trap or impede anything else. Whether you use a simple gauge or an air-integrated computer is up to you, but if you don't want to buy two depth measuring devices, putting the computer on your left hip will mean you can't watch it during ascents and descents unless you hold it, which ties up a hand -- and that's awkward, for example, if you are hanging onto a line in current AND trying to manage your BC (and dry suit, in my case). My husband uses an air-integrated computer instead of a gauge, but he uses another depth gauge on his wrist.
I use my compass on my left wrist, but I think this is one place where you can argue where something ought to go. A compass on the left wrist requires that you be VERY careful with compass positioning, if you are needing to swim a heading that someone gave you, because it's easy for the compass to end up off to the left of you, and result in an erroneous course. (If you are taking a heading on something yourself, the error is probably going to be consistent enough not to bother anything, or at least that's my experience.) A compass clipped off in a pocket can be brought out and held directly in front of you, but is more susceptible to loss. A compass on the end of a console can be just as difficult as a wrist compass to get into the right position, unless the HP hose is so long that you have a great big bow in it when it's clipped off, which can be an annoyance in rocks or kelp.
I like my equipment streamlined and close to my body. I like my gauges accessible, and I don't want to lose them. So I use a short HP hose, a simple pressure gauge, and wrist compass and computer. Works for me.