I am curious, as we all know GIII coins are plentiful, but are the denarii or tets more abundant? Especially in higher grades?
I don't fully understand the question, but the denarii, while scarcer than the Ant's, are fairly affordable, and one can get a quite decent Antioch tetradrachm, like I did when giving a birthday present.
Don't forget the sestertii! I paid 65 pounds for this (minus fees). The coin is much nicer in hand, a nicer green than the photo suggests.
I don't know the answer, either, but this antoninianus didn't put me back very far. Gordian III coins seem pretty affordable overall in general, so it's difficult to say.
You can find your answer here: https://discovery.ucl.ac.uk/id/eprint/10116536/1/Bland_thesis.pdf and everything you could ever want to know about Gordian III coins. The denarii are the most scarce; less than 1/2 the production of antoniniani. The reason they are more scarce is they were only minted while he was a Cesar. When he became emperor they switched over to antoniniani. There are also Gordian III tetradrachms that were minted in Antioch, Syria which are more scarce than the denarii and antoniniani. Here are some of my Gordian III's:
The antoninianus was created under Caracalla, probably in 213 or 214. This coin was officially worth 2 denarii, but contained only 150% of a denarius' silver content (roughly). With the same amount of silver the imperial mint could produce 30 denarii or 20 antoniniani worth 40 denarii. There was a problem with these coins. Caracalla, Macrinus could have minted a majority of antoniniani, but they are relatively scarce: these emperors minted a majority of denarii. Their successor Elagabalus stopped the production : there are antoniniani of Elagabalus dated 218 and 219, but no 220, 221 and 222. There are no undated specimens on which his portrait would be bearded. We can say Antoniniani were abandoned c. 219. There are no antoniniani of Severus Alexander or Maximinus. Suddenly the production resumed in Rome in 238, under the short-lived regime of Balbinus and Pupienus, and their successor Gordian III mass-produced them, while denarii were becoming scarce.