Ok I'm looking at an acr by a&k it's 280 is it worth it

Yes, better then Magpul, for the price.

Because I'm gettin 160 for my birthday and I'm going to save the rest for it will it last me a while

No it is not worth it. There are better performing guns in the same price range and cheaper. The A&K Masada has a slightly proprietary gearbox I believe so it's not 100% upgradeable. Also while some people say it has to be tuned before you play with it, they are wrong, you don't need to tune it, but if you don't then it's performance won't be very good.

I love my A&K Masada,
Shoots true for a good estimated 140ft (not a stock hopup however)
I also have it re wired to the rear and with both deans and tamya connectors
Sure you can get a "better" gun performance wise for the price. But the quality of the Masada is amazing, needs very little upgrades to make it great. Its got a solid FPS so all you really need is a good hopup and barrel. Im running a CNC full metal hopup unit myself.
The stock is fully adjustable and solidly locks in place, The bolt catch functions as well.

You know with that extra 250 bucks, you can make a gun that shoots A LOT BETTER than the magpul ver.

The Magpul physically feels better in general when compared to the A&K
Performance out of the box, again Magpul performs better.
Now as stated previously. The A&K is about $250 cheaper, and honestly simply putting $150 into the gun will have it perform better than the Magpul model and you can use the extra $100 for mags.

It's honestly the route I'd take if I were interested in the Masada. Even if you don't know about internals, I'd recommend you use the gun for about a month, then take it to a tech and get it upgraded. I say a month so you know how the gun feels, no sense upgrading what you don't like externally.