Buy something FOR someone

The other day you showed me this sentence:

那天你给我看这个句子：

I have bought some gifts to my parents for Chinese New Year.

我为我父母买了一些春节礼物。

I understood that you wanted me to see if your sentence was grammatically correct.

我明白你要我看看你的句子语法对不对。

When I was typing my reply, you sent me another message:

当我正在打字回复的时候，你发来了另一条信息：

You said: The fact is that I have not finished shopping.

你说：事实是我还没有完全买好。

Despite seeing that second message, I did not realize your real concern was about the use of the perfect tense when your shopping was incomplete.

尽管我看到了那第二条信息，我（那时）并没有意识到你真正关切的是关于 在购物未完成时 用上了【完成式】。

I neglected that because the use of the perfect tense there...... was perfect!

我忽略了那个问题因为【完成式】用在那儿正是完美的呀！

Yes, you had more shopping to do, but your sentence was about those gifts that you had already bought. So, it was correct to use the perfect tense.

没错，你还要继续买礼物，但是你的句子是关于已经买了的那些礼物。所以，用【完成式】是对的。

That day, what I did tell you was that you needed to change the preposition TO to FOR:

那天，我有告诉你的是你必须把 TO 这个介词换成 FOR。

You asked suspiciously: using FOR twice? I said yes.

你怀疑地问：两个都用 FOR 吗？ 我说是。

Then you sent me a vivid emoji GIF: a frog with palms up saying "all right" reluctantly.

然后你回我一个传神的动态表情包：一只青蛙摊开双手勉强地说“好吧”。

I guess you were not exactly convinced because your original sentence had a deceptive correct “sound” to it. But that was an illusion.

我猜你并不完全信服，因为你的原句听起来有个误导人的“对的样子/声音”。但那是一个错觉。

This illusion is caused by the fact that “bought” and “brought” have a similar pronunciation and they look alike too.

这个错觉是由于 bought （买了） 和 brought （带了） 读音相近, 而它们的字形也相像。

你看看：
Have a look:

这个句子是错的：
I have bought some gifts TO my parents FOR Chinese New Year.

这个句子却是对的：
I have brought some gifts TO my parents FOR Chinese New Year.

But, what you meant to say was about BUYING gifts, not about BRINGING gifts. So, in order to correct the sentence without changing the structure, the preposition TO should be changed to FOR.

可是，你要说的是关于买礼物，不是关于带礼物。所以，为了要把句子按照原本构造改成对的，那就得把介词 TO 换成 FOR.

But of course, using FOR twice in a short sentence such as this one sounds ugly. To avoid such repetition, we can change the structure of the sentence:

但是当然，在一个像这样的短句里连续用两次 FOR 是难听的。要避免这样的重复，我们可以把句子的构造改一改：

I have bought some Chinese New Year gifts FOR my parents.

You see, it is much more concise now.
你看，这样的说法简洁得多了。

Finally, to reiterate:
You buy something FOR someone, and not TO someone.

最后重申：
买东西给某人是 buy something FOR someone, 不是 buy something TO someone.