If you are looking to buy only one I'd look at the Silencerco saker 7.62. It is extremely modular and will work with just about any firearm you may want to use in the future. It is a QD mount of can be direct thread. Also you can put a 5.56 end cap on it and it is then quieter than their 5.56 Saker. If you want something light weight look at Crux suppressors titanium cans. Their quality is top notch.
They now have the omega which is 6 ounces lighter. Saker is the choice for full auto options. Maybe not so much on the omega though, in case you were headed that route.