一个高二学生想出国读书

You better choose a country with English as its mother tongue, not as a second language like Singapore or Netherlands, etc.
1. U.S. is the best. New Zealand is the cheapest.
2. You have to ask each country's embassy for details.
3. Toefl score might help. But you can also take an English course in that country.
4. It depends. If you love to live in that country and your English is good enough then you will probably earn a lot more than you earn in China.
Hope my answers will help. Wish you good luck !

新西兰吧
我和楼主一样...我是高二出国的。今天考上了奥克兰大学...世界top50的学校，很不错的。我是学教育，毕业后的话...老师可是全世界都长期短缺的职业，尤其是数学老师...前景应该不错的。

首先就是要准备资料，比如护照，公证，另外还需要联系学校。

等学校的offer下来之后，讲材料以及体检报告递交移民局就可以了。

体检报告可以等签证预评估下来之后再交。

最后等着签证下来，准备出发就可以了！

我没别的意思，但是那个排名。。。真的很离谱。。。

你问的太宽泛，建议先去论坛看看，或者在百度搜索下，会明白很多。
个人的情况都不一样，很难能够回答。
要具体看你去读什么，什么时候走，家里条件怎么样，个人能力怎么样，去哪个国家……