Gokai also means five seas. Go=5 and Kai=Sea

Does anyone know what ToQger means in English?

Tokkyu means "Express Line."

Ressha Sentai Tokkyuger (ToQger) means, approximately, "Fierce Train Squad Express-Line Ranger."

Male or Female Yellows, which ones do you prefer?

Can Super Sentai have American casts alongside with Japanese Casts?

I prefer yellows to be male and whites to be female.

I'm sure they can, but I don't think they have. All of the American characters in sentai that I've seen have been Japanese guys (dressed like cowboys). One of the episodes of Ninninger had the Japanese cast member from Dino Charge as a civilian though, and he even spoke English

That's cool. The idea for Super Sentai Fan-Fiction that keeps coming to my head was an American Male, Caucasian, 22 years old from Los Angeles, California who became the Black Sentai Ranger but as a 6th Sentai Ranger

Kyoryuger had a caucasian ranger. However I don't think Ramirez was that popular since there was not much merchandise for Kyoryu Cyan from what I can remember.

He was never intended to have much merchandise regardless of popularity. But he was pretty popular for a caucasian actor in a japanese kids show. In an interview a while ago he said that a lot of Mothers came up to him while he was on the show and told him that hes their kids favorite.