What opening should I learn?

For either white or black.

As white I can play:

1. e4: I primarily play the Ruy against 1... e5 though I can play the Italian, and open sicilians (English attack)against 1...c5

1. d4 Queens gambit.

1. Nf3 (current personal favorite) where I try to transpose into one of the three systems above. 

As black I play:

Old Sicilian against 1.e4.  I don't play the dragon.

... Nf6 against 1.d4 where I can play either 2... g6 or 2... d5 against mainlaine 2.c5

What should I add to my repertoire?  Do you think I should I investigate other openings for white or concentrate on the ones I know?  If the former, which would you recommend?  As black should I learn the Caro-Kann or the French, or should I look into playing dragon variants of the sicilian?

On a similar note, what are some good opening gambits to learn? 

Blackmar-Diemer gambit my favorite ;)

(and is it good or bad well....)

Thanks... I will definitely start playing that.