looking to modify my AR with a free-float fore guard looking for something nice light weight good construction but not to over the top pricing.  started my search on Amazon but am expanding it before I buy.  any advise would be greatly appreciated.

 

Whats your budget, how long is your barrel?

My favorite so far:

Troy Industries VTAC Alpha Battle Rail Modular Free Float Handguard

http://www.midwayusa.com/product/3058317644/troy-industries-vtac-alpha-battle-rail-modular-free-float-handguard-ar-15

Midwest has some lightweight FF rails.

https://www.midwestindustriesinc.com/index.cfm?fuseaction=category.display&category_ID=450

ALG Defense

I'll second the Troy Industries rails

Midwest Industries // M-Lok 

For the weight and price Midwest Industries cant be beat

 I like the Midwest Industries SS Gen 2 tubes. They're 1.5 inches in diameter, rather than 2 inches, which was more common a couple years ago.
Depends what kind of operating system you have, too. DGI will require a low-profile gas block (unless you leave it exposed, which means removing it, installing the forearm, then replacing the gas block).  My LWRC M6A2's piston drive won't clear a 1.5-inch handguard.
Also, you should decide whether you're willing to replace the original barrel nut in order to mount your new handguard. The Midwest Industries tubes come with a replacement  nut made specifically for their tubes. 
Some other brands use the stock barrel nut, e.g. Samson, Rainier Evolution.
And there are factors to consider about the length of the handguard. You probably want something long enough to cover the gas block, but that depends on what length barrel (and gas system) you have. A lot of folks favor forearms of 12 to 15 inches so they can follow the latest fashion of fully extending their support arm. (I ain't one of em) But more length means more weight and ounces add up to pounds.
And finally, you probably want to consider the M-Lok and Key Mod attachment systems.  Kind of like VHS and Beta. You can choose one, or wait to see if either one fades away, or just ignore that issue altogether.

Good luck with your research. The more you read up, the less money you'll waste on crap that ends up unused in your parts box, at least until the next fad change. Quadrails, anyone?

http://algdefense.com/rails.html 

I'll second the Troy Industries rails

Had a Troy TRX rail but never got it installed as the barrel nut (,308) was not cut right, threads far too tight.  Could have ruined my receiver putting it on it was so tight.

Got a new nut but chickened out trying that in case it had the same problem, preferring to sell it unopened for what I paid for the thing, and going with a new MI SS.  Got on a weight reduction kick and the Troy was not any lighter than the DPMS vented tube I had on there.

I love the super slim profile of the MI SS in lieu of the usual fat handguards everyone else has for the .308.

I use the standard rifle length so to leave the gas block exposed.  The current trend of covering the block is all the rage, but I find it dumb if you use open sights.  Front sight on a handguard far too easy to knock out of alignment..  I just use a popup gas block mounted sight on a gas adjustable block. 

KAC URX 4, Noveske NSR, Geissele

As the guy said above you want to consider the length.  The longer the handguard the more of that 3gun grip you can get, but it is also good for resting your rifle on things when your behind cover and not your barrel.  Ergonomics are important too; what feels good toYOU.  Will you be attaching a bunch or crap? (hopefully not, the whole purpose of the new systems are to save on weight, all you need is a light).  Think about what attachment system will work best for you, M-LOK, Picatinny, KeyMod.  If the rifle is important to you and something you are going to keep around as a tool, you may want to save up on a couple of paychecks and buy something bombproof (non-clamping on the barrelnut. do your research, I won't namedrop).  Good luck.

It's not he cheapest but the BCM KMR it one of the lightest rails I've ever handled. I have a 15" and its air light.

I have the troy alpha, MI quad rail, and Sampson evo. I like that the troy and evo use the stock barrel nut and both are very light. On a budget, I'd say evo cuz they are cheaper, super easy install, and come with 3 rail sections.