English is my second language. Where do I start?

In general, you will be better off writing in the language you’re most comfortable with. Don’t forget, any language can reach hundreds of thousands of people at least. The English language part of the internet is vastly over catered for, so depending on your language, it may even be the case that you can be a “big fish in a little pond”.

Once a book has become popular with your native language audience, there is always the option to get a translator at that stage in order to reach the large US and UK markets. Doing it this way round has the benefit of only needing to pay the substantial translation costs once your work has proved itself commercially, therefore being much less of a risk.