Game programming requires you to have nice base in whatever language you choose. Even if you dont know everything, if you know the basic concepts and a working knowlwdge of various APIs then things will be much easier for you.
If you are just beggining to program, you will soon be frustrated as you will not be able to understand loads of info you might find and the work you do wont be very effiicent and you may end up reinventing the wheel and unessearly doing code, which might have been done in a much better way if you knew the language properly.
If are going for C++, you should know the basic concepts like, functions, structs, classes, templates, STL. Operator overloading,dynamic mem management, then Win32 api, basics of using OpenGL or DX or SDL, OpenAL or FMOD.
Take my advice, learn C++ properly. If you have a book, finish it from start to finish. Do a few simple projects (in console) which involve concepts like file handling, link lists, vectors.This will give you a feeling of designing a program.
Then move on to using the Win32 API. You will have a few headaches to start with, but you should get along fine.
Then you are ready, helps if you have a little knowledge of STL, to start looking for game programming info.
Then you have just taken a step into a new dimension, where your way for thinking will change so much, because game programming in an advanced application of programming.
I would estimate you will take around a year to get C++'s basics. You might read the book faster but programming is quite an art and it takes experiance before you will be able to work fast, and code well.
I've been game programming for around 2 years now, and I've learnt a lot, maybe 20 times, that of what I learnt when I was learning C++.
I wish you best of luck, and be patient.