Gambling is not good and never recommend so you should learn the english conversation how to refuse people when they ask you to bet on something. Also, somtimes we don't have to take it too serious because it's just a fun topics among friends.
Example 1
You : Do you think Sonics will win the game tonight?
Friend : I don't think so. They are not good enough tonight.
You : You wanna bet?
Friend : Yeah? How much do you want?
You : Let's make it 30 Dollars!!
Friend : Alright. I'll go for it.
Example 2
You : Do you think Sonics will win the game tonight?
Friend : Not a chance. Spurs will kick their butt.
You : Let's put some wager on it?
Friend : No sorry. I don't do gambling.
You : Wow. You are one of a kind.
Example 3
You : I am sure Mike Nadal will win again tonight
Friend : Oh really? I don't think so.
You : Aha? You want to bet?
Friend : Sorry, I don't do gambling.