Gokaiger, Gekiranger, Abaranger, Shinkenger, and Zyuohger are good options.

Jetman or Zyohger depending on if you're wanting to start with something pre MMPR or post MMPR.

I definitely recommend Jetman, Dairanger, Megaranger, Timeranger, Gekiranger, Magiranger, and Gokaiger. Zyuranger isn't a bad series to serve as your gateway into the franchise overall either since that is the case with me.

From the 80s, Bioman, Flashman, Liveman. 90s Jetman, Zyuranger, Carranger, Megaranger, Timeranger. 2000s Gaoranger, Hurricanger, Gekiranger, Shinkenger. 2010s Kyoryuger, ToQger, Zyuohger. And 2020s Kiramager.
As for Gokaiger, watch after seeing at least 3 sentai shows because it is fan service heavy so it is better after being accustomed to the franchise.

I would suggest anything from Jetman-Hurricanger since those are legally available to Western viewers. I also agree with Sunred about Gokaiger as it's meant for those who have a well developed knowledge about the franchise.

Gokaiger was meant for kids who had at best seen the last few episodes of Goseiger, as with every Sentai. It's perfectly good standalone and was my first Toku

Yeah, Gokaiger was my first Sentai too, and it can absolutely be enjoyed without a deep understanding of the franchise's history.

Really, as the flood of completely different recommendations here suggest, I don't think there are many bad choices for an introduction though?

So, if Ultraman is able to get Kane Kosugi, does that mean there's the possibility that Sentai could afford him, too?

After rewatching some Carranger, I started wandering about an extra. In the debut episode of VRV Robo, we see VRV Master go about his daily routine on Earth which includes visiting a regular barber. However, he notices that the barber's demeanor and actions aren't right and the barber chats a moment before revealing himself to be RitchiRitchihiker! Is the barber actor the actual VA for RitchiRitchihiker, in a live cameo? Granted, they could've just dubbed the voice of RitchiRitchihiker over the barber actor, but I don't really think that was the case here.

Yep, I think you are correct acording to his filmography.