For Father's day this year my Dad gave me the task of making his pistol more reliable. He likes to shoot cheap bulk ammo and he gets a lot of stovepipes and some feed issues, probably every other mag on average. The gun is basically stock except for a Volquartsen exact edge extractor that I put in about 2 years ago. I'm guess that upgrade cut the failures in half but I don't have any data. My first step is to completely strip the gun and take the mags apart and give them a good cleaning. Then I plan on buying various types of ammo to see what it likes.

My question for the internets... do you guys have any suggestions as to what kind of ammo this gun likes? What are some mods that I can do to make this pistol more reliable?

Thanks in advance.

Clean it well, especially the chamber. Clean the magazines. Try it with a couple different types of ammo, sometimes a particular gun will not like one type.

I have ran thousands of rounds of Federal bulk ammo through several MKIIs for years. Other than a very few rounds that were duds the only problems I have had were due to fouling.
Remove the bolt and look at the bolt face. I have had carbon build up under the extractor that caused the empty case to be pushed to the side away from the extractor. That would cause the empty case to jam against the next round being fed.
There is also a recessed notch next to the chamber. If that gets full it will cause the same problem.
You should also check the barrel and chamber for lead fouling. Some ammo, especially Remington, uses soft lead and will foul the barrel quickly.