'I gotta' is grammatically incorrect. It is more of a spoken form. If you want to say this with proper grammar, the equivalent would be, 'I have got to' or 'I've got to'. In the spoken form, 'got to' is shortened to 'gotta' and the word 'have' is dropped. 'I gotta'是语法错误，它更像是一种口语形式，如果你想要用正确的语法来说，就相当于'I have got to'或者'I've got to'，在口语形式里，'got to'是'gotta'的缩写，而且'have'这个词省略了。

Here are some examples: 这里有一些例子： 

"I gotta manage my money."

 我必须要管理好我的钱。

"I gotta obey the laws."

 我必须要遵从法律。

"I gotta move to a bigger house."

 我必须要搬到更大的房子里去。

"I gotta impress my boss."

 我必须要让我的领导对我印象深刻。

"I gotta brush my teeth."

 我必须要刷牙了。

By adding the word 'have' you can change what you are saying to express something that needs to be done in the near future. 通过加'have'这个词你就可以改变在不久的将来你需要做的事情所要表达的东西。
Here are some examples: 这里有一些例子： 

"I have got to be on time to work."

 我必须要准时上班。

"I've gotta try harder at school."

 我必须要在学校更努力地学习了。

"I've gotta tell my wife I'll be late."

 我必须要告诉我妻子我会迟到。

"I've gotta learn more about the laws."

 我必须要学习更多关于法律的知识。

"I've gotta clean my house today."

 我今天必须要打扫房子。