As of now, best offer i know of is the deposit $500 get $250 in Bonus Bets. Make an account, then call up asking about what offers they can give you. You should get offered the 500 for 250.
As for turnover requirements, it never used to be on spread betting. I am unsure if that was always in the Terms and conditions, or it’s something new that has been added. Be sure to ask about that once they have offered you the 500 for 250.