Aside from guns (in the range bag) and ammo (in a separate bag), and targets (carried separately), my range bag remains packed at all time with the following so that I merely have to pull whatever I am practicing with that day and its ammo:
Keys for the locks on the gate (it is members only)
Range membership card
toilet paper
hand sanitizer
cleaning kit with rods, jags, brushes, patches, rags, Break Free and Q-tips
Glock Armorer's tool (I am a certified armorer)
Set of gunsmithing screwdrivers originally bought from Larry Potterfield when he worked behing the counter of his first little gun store just west of Columbia, Missouri - Bonanza is the brand of screwdriver set, made before Forster bought them out
1911 bushing wrench
hex keys
punch sizes for full take down of 1911
plastic mallet
Wilson multi-tool
Stapler and extra staples
My ear muffs (not collapsible type) and two extra of the collapsible type in case I take a new shooter or someone that does not have their stuff with them
extra pair of shooting glasses
Uplula loader and Glock mag loader
full moon clips for N frame .45 ACP
A few ziplock bags for storage of any carry ammo that is removed from a pistol prior to range work with target ammo
The range bag ALWAYS has an old Ruger 22 Auto in it, and the ammo bag always has a brick of 22 LR high velocity 40 grain solids. Other than that, a gun and appropriate ammo has to be added to the package.
Other than some Break Free occasionally applied around the breech face, feed ramp, extractor and to the bolt when the slide is locked back, and an external wipe down of the pistol and magazines, the Ruger has never been cleaned, ever, in many thousands of rounds and it has never malfunctioned. It is a good thing the Ruger is so reliable, because they are nearly impossible to field strip for cleaning, so I just don't.
In addition to the foregoing, a very old 10-22 also goes along so that I can get some trigger time with a long gun. It never has been cleaned either, although at about 15 years, I found I had to tighten the stock screws. But that was 10 years ago or so. It is little things like that that the basic little kit of tools is used for at the range.
The range bag and ammo bag are the deluxe models from Elite Survival Systems, and while there may be equivalent cases out there, I am quite certain there are none better.