It's recommended that you read a lot when you're learning Spanish. Or any language for that matter. I think that's good advice. In fact, that's how I came across this little gem - ¡Puedes hacer lo que te dé la gana!
Before we translate this sentence, let's talk about a nifty little expression...Dar la gana.
Dar la gana means to feel like doing something. Let's look at some examples...
¿A dónde vas? ----- A donde me da la gana.
Where are you going? ------ Wherever I feel like.
No me da la gana hacer eso ----- I don't feel like (want to) do that.
Haz lo que te de la gana ---- Do whatever you feel like
¿Que vas a hacer? ----- Lo que me de la gana.
What are you going to do? ---- Whatever I feel like.
Now let's get back to our original sentence:
¡Puedes hacer lo que te dé la gana! ----- You can do whatever you feel like.
Antes de que se me olivido (before I forget), una cosita más. The dar in Dar la gana of course has to be conjugated, and there's a very interesting thread in WordReference that discusses the correct conjugations when using this phrase. Click here to read it. It's in Spanish, but I think a good read if you're able or up for the challenge.
I think this falls into that category of useful Spanish that I promised to occassionally touch on. Hopefully my explanation and the examples have given you enough to understand and start using this phrase.