Since free play doesn’t count towards points it is important to first try to convert these free play into real money.  There are different strategies for that.  

You can use that Free Play to do some Advantage Play however make sure that when you win back some money that you “Bank” it instead of using it and instead use more Free Play till all the Free Play has been converted.  Over time Carnival will give you from $100 Free Play to $1,000 and even $2,500 which adds up to a lot of points if you do not first convert it.

You can use that Free Play at a table and play Red and Black for example at roulette to convert a maximum of Free Play but you will loose some to the 0 and 00.  To play that Free Play at the tables ask the cashier to give you “Chips” instead of loading it into a slot machine.

Some ships in the fleet give you the Free Play directly as cash so this may be a criteria of selection for you if you book a cruise with just the intent to maximize the money made with Advantage Play.  The Elation, Freedom, Glory, Legend, Liberty, Miracle, Paradise, Pride, Splendor, Sunshine, Valor give you Cash for Free Play.