Improve the bracketed part of the sentence.
I plan to get started (as soon as I could).
The sentence uses the verb ‘could’, which is incorrect.
The 2nd option is incorrect because the word ‘may’ changes the meaning of the sentence.
The sentence is trying to convey that the first person plans to get started as soon as he can, but in the 3rd option the first person has changed to second person, which is incorrect.
The verb ‘could’ is the past tense of ‘can’. Here in this sentence, we need to use the present tense ‘can’.
Therefore, the correct answer is option 1.
Improved sentence – I plan to get started as soon as I can.