my iphone 6 plus 64 gb didn't come with pre-install apps like imovie or garageband or something.. what can i do now ?

iMovie and GarageBand are not pre-installed on an iPhone. You can buy them through the App Store. $4.99 each in the U.S.

https://itunes.apple.com/us/app/imovie/id377298193?mt=8

https://itunes.apple.com/us/app/garageband/id408709785?mt=8

I sell iPhone all day and the 6 and 6+ do come with them

These apps are free for you, but the Apple tech spec page seems to say you have to login to the App Store to download/register them, so you'll need an Apple ID First.

http://www.apple.com/iphone-6/specs/