[Tokumonkey]

I don't know that I'd start with Gokaiger. It was my first Sentai, and I kinda enjoyed it, but halfway through, I put it on pause and switched to another show because it just wasn't working for me. I eventually finished it, but was underwhelmed.

After seeing a number of other series, I came back to Gokaiger, and once I had context for past Sentai series, I was sort of gobsmacked by how good it is.

If I were choosing a show for the first time, I'd probably go with Gekiranger. I utterly loved Kyoryuger, but your mileage may vary on that.