The original 9mm Luger load is reported to have been a 124gr FMJ at 1050fps from the 4" Luger.
A few years before WW I, the load was changed to a 115gr FMJ at 1150fps. This is what a WW I Luger should run on.
I have run my 1936 mismatch on American Eagle 124gr and 115gr with few problems. NOT "no problems" few problems, mostly feeding, which right now, I feel are magazine issues.
Stay away from the guy who says you need HOT SMG ammo to run a Luger. Stay FAR away!!!!
Most "modern" loads are not good choices, particularly anything loaded with a JHP. #1 the Luger was never made to feed hollowpoints. Some will, many won't, yours might. #2 JHP loads today are intended for personal defense and are loaded warmer than what I am comfortable with for a Luger.
AVOID EVERYTHING marked +P!!!!
A matching 1916 Erfurt is a sweet gun, but shooting the now 100yr old beauty is always a risk, even with the right ammo. If you break one of the numbered parts (like the firing pin, for example) you have just turned a $2000+ collector Luger into a $1000 +/- "shooter" Luger.
The safest thing to do, value wise, is to get replacement parts for all the numbered parts you can, and install THOSE parts into the gun for shooting use. If one of them breaks you still have an all matching Luger when you put the original parts back in.
The toggle action design is very efficient and pretty strong, BUT the rest of the parts aren't that strong, and with a few rare exceptions, the newest ones are over 70 years old, with many over 100. The metal isn't what is used today, plus what ever it has gone through over the years means things break, even under what is proper and period correct conditions (like using the right ammo). It happens. And of course when you go beyond what the gun was built for, the breakage rate goes up, DRASTICALLY.
Get some American made "plain jane" ball ammo, something with a listed velocity in the 1100fps range. NOT military surplus ammo! And not European military ammo of any kind! I say this because there is no guarantee that the surplus ammo is what the package markings say it is.
One friend of mine had his High Power battered to the point the locking lugs were being peened, because he shot 9mm "surplus" ammo that was much hotter than what his gun was made for, but not marked as such in any way. And, IIRC it was only a couple boxes of the stuff that damaged the gun.
NOT something to put in any Luger!!
Carefully worked up handloads might be your best option, if suitable commercial ammo can't be easily found.
Good Luck!