"I eat a lot."
So, omitted 私 and that is wrong somehow? I omitted it because it seemed obvious.
its not wrong to omit it, however it must be clear from the context that you are talking about yourself otherwise the meaning of the sentence might become confusing. Its like in spanish how you can omit 'yo' for example 'yo como pan' would be the same as 'como pan' and it works like this in japanese too
Looks like this has been fixed. I left it out and was correct.
Would adding a を before 食べます make it incorrect? Would it sound unnatural?
Yes, that would be wrong.
を is used to indicate the direct object of the verb, which in the case of 食べます, would be the thing that you're eating. For example:
「りんごをたくさん食べます。」"I eat lots of apples."
As it doesn't specify what you're eating here though, there isn't any place for を in the sentence.
Why is there 外 in front of the sentence? The sentence isn't "I eat a lot outside" so why is this there?
Ah you have misread, it is 私 not 外.
I dont know why people are downvoting you, you just misread it...