I'm going to offer a contrarian viewpoint: Go for it.
My understanding of the Dhamma is that whatever stage we find ourselves at, there is an opportunity right there in that moment for greater wisdom. Ambition is a complex thing. Most of us, if we are not arahants, will have some degree of ambition. Ambition can be a mix of lots of different things, including (as you correctly point out) a desire to help others. Blended with that desire to help others, you might also find some selfishness mixed in (as Retro correctly points out).
But the point is not to kill the ambition that arises in this moment. That, according to my understanding, is contrary to Dhamma practice. Rather, the idea is to recognize amibition as it arises, identify its causes and conditions if you can, understand its nature, and in that very moment do the right thing to the best of your ability.
Sometimes the right thing to do might be this: to make a great film.
But another thing to bear in mind is that ambition (that blend of stuff that will arise whether you want it to or not) doesn't have to be fed. You don't have to identify "ambition" and try to force it to come, or strengthen it, or anything else. Just leave it be. Let it be.
That's the way it is with these kinds of mental phenomena. We have this incorrect notion that we are in complete control, that somehow "I" am ambitious, "I" am kind, "I" am angry, "I" am intelligent. That's all hogwash. None of that stuff is you. Each of those phenomena -- ambition, anger, kindness -- has its causes and conditions. Each will come up of its own accord based on past and present kamma. You don't have full control of any of that stuff. But, with wisdom, you have some control over what you do in this moment no matter what mental condition happens to arise.
Forget about what you think "meditation" might or might not accomplish. It's impossible to separate out meditation from all the other stuff that you do the rest of the time, like right speech, right livelihood, right effort, etc. If you really want to meditate effectively, then knock off the booze, treat everyone as if you love them, be kind to yourself, bath, smile, and so on. In other words, don't isolate meditation and put it on some kind of pedestal. Do meditate. Don't worry about it.
Ashitaka, I'm no teacher, and I'm not even a very good meditator. But I do know you will get a lot better advice if you go to a teacher you trust and share your practice struggles with him or her.
Regardless, be encouraged. Do your best in each moment, applying whatever wisdom you can. It will work out.