N2
次第だ・次第で
しだいだ・しだいで
Depending on, So
夢をかなえられるかどうかは君の努力次第だ。
Being able to make your dream come true or not depends on you.
Explanation
「次第だ・次第で」 has 2 uses
1Depends on
After a noun: the outcome depends on it: 「成功は努力次第だ」 (success depends on effort). Mid-sentence: 「次第で」「次第では」.
ワインの渋味は濃度次第だ。
Wine's astringency depends on its concentration.
夢をかなえられるかどうかは君の努力次第だ。
Being able to make your dream come true or not depends on you.
2That is why
At the end, 「〜次第です」 explains how things came about in business letters and reports: 「このような理由でお断りする次第です」 (for these reasons, we must decline).
担当者が急病のため、私が代わりに参った次第です。
Our person in charge suddenly fell ill, which is why I have come in their place.
予定が変わりましたので、ご連絡した次第です。
Our plans have changed, so I am writing to let you know.
Mixed up with
「noun+次第だ/次第で」: depends on.
「verb stem+次第」: as soon as: 「決まり次第ご連絡します」 (I'll contact you as soon as it is decided). The end of the sentence cannot be past tense.
「sentence+という次第だ」: 'that is how it came about'; official wording.