I'm just looking.

我只是随便看看

A: Can I help you, sir?

A: 先生，我能帮忙吗？

B: Thank you. I'd like to look at jackets. Where is the men's clothes department?

B: 我想看看夹克衫。男士服装商场在哪里？

A: Over there, sir. On the left.

A: 先生，在那边。

B: On the left. Thank you.

B: 在左侧。谢谢你。

A: I can show you some jackets, sir.  What kind of jacket would you like?

A: 我可以给你看看几件夹克衫，先生。你想要哪种夹克衫？

B: Thank you, but I'm just looking at the moment.

B: 谢谢你，但是我现在只是随便看看。

Notes 注释

1. Shop assistants can offer to help customers, for example:  I can show you some jackets, sir.  / I can show you some jackets, sir. They will ask you what you like:  What kind of jacket would you like?
商店的服务员会主动提出帮助顾客买东西，例如：  I can show you some jackets, sir.  /我可以给你看看几件夹克衫，先生。他们还会问你想要什么样的：What kind of jacket would you like? /你想要哪种夹克衫？

2. If you want to look by yourself before buying you can say:  I'm just looking at the moment. / I'm just looking at the moment.
如果你想在购买前自己随便看看，你可以说：I'm just looking at the moment. /我现在只是随便看看