The best way to learn proper English is to read news report, and watch news on TV. Watching TV shows is a great way to learn casual English, slang words, understand culture reference and humor. If you have already watched these shows then you may recall the words used in the following dialogs.

You're intimidated by Amy's intellect.
To that, I say BUCK up.
The Big Bang Theory Season 4, Episode 3

but deluxe detailing
is the best for your BUCK.
Breaking Bad Season 4, Episode 9

Those are BUCK.
Breaking Bad Season 2, Episode 5

There's gotta be other ways
you can make a quick BUCK.
The Big Bang Theory Season 10, Episode 17

and all you've got is "Buck up"?
The Big Bang Theory Season 5, Episode 1