Spinner is a casino term used to refer to a winning streak.
While the exact origin of the term is unknown, it is believed that it came from players going on long winning streaks while playing roulette or slot machines. Namely, playing slot machines involves spinning of the reels while in order to play roulette, a croupier must spin the roulette wheel. Some people thought that lucky players in question were able to manipulate the wheel or reels, which is where the term allegedly comes from.
Regardless of the origin of the word, if someone calls you or your streak a spinner, they are praising your winning streak.