N3
ばいい
Can, Should, It'd be good if
どれを食べればいいか迷ってるところ。
I'm a little lost as to which one would be good to eat.
Explanation
「ばいい」 has 3 uses
1Just do this
Says that doing this is enough, or gives easy advice: 「辞書を引けばいい」 (just look it up).
運動をすればいいだろう。
It would probably be good if you exercised.
テストでいい点を取りたかったら、勉強すればいいんじゃない？
If you want a good grade on your test, shouldn't you just study?
2Asking what to do
With a question word, asks what you should do: 「どうすればいいですか」 (What should I do?).
どれを食べればいいか迷ってるところ。
I'm a little lost as to which one would be good to eat.
それいつまでにやればいい？
When would it be good to do it by?
3If only…
With 「のに」 or 「けど」 after it: 'if only…', a wish or regret that it isn't so.
行ければいいけど、行けるか分からない。
It would be good if I could go, but I don't know if I can.
眠たいならちょっと仮眠をとればいいのに。
If you're sleepy, you could just take a short nap.
Mixed up with
Add 「のに」 (「～ばいいのに」) and it means 'I wish you would...', with regret or mild blame that it wasn't done.
「～たらいい」 is more casual: 「どうしたらいい？」. 「～といい」 is mostly a hope: 「明日晴れるといいね」 (I hope it's sunny tomorrow).
「～ほうがいい」 is firmer advice after comparing options and can sound rude to elders; 「～ばいい」 is softer.