I have crooked yellow teeth, how do I fix them? Braces or veneers? Which is better? (Photos)

From the photos you provided it looks like braces or Invisalign should be able to straighten your teeth properly. Although veneers may be the faster option I strongly urge you to use orthodontics followed by whitening if the white spots are a concern. If you are still not happy then veneers can be done but I would try the more conservative option first. It is tough to say how much it will cost as every area is different although the braces and veneers are likely in the same ball park.

I would suggest straightening the teeth before anything else is done. After they are straight, you can decide if you want to whiten or have veneers. I wouldn't recommend veneers on the teeth in the position they are currently.

Get your teeth straightened with braces or Invisalign first. As far as the color of your teeth and white spots, try bleaching your teeth to whiten and if the white spots are still noticeable, have your dentist use a very conservative white spot removal gel. After this treatment is completed, you may not even need veneers. It's best to stick to conservative, minimally invasive treatment, because once your teeth are prepared for veneers, you are in for a life time of dentistry. 

Hi:For best result, you should straighten out your upper front teeth with invisalign and then get porcelain veneers to change the color of your teeth.Best,Dr. Maddahi 

You will get the best, healthiest result if you straighten your teeth first with braces or Invisalign.  Then if color is still an issue, porcelain veneers can be done in a uniform thickness with minimal preparation and will give you a great smile.  Your lower teeth will also be straight and easier to clean and maintain gum health.