Getting 'involved in long range shooting' needs some parameters in order to attempt to answer your question.
As suggested above, what are the distances that you feel are appropriate for your long range desires?
Entering into long range target shooting and hunting usually involves that money pit which pushes most of us to spend a lot more than we anticipate. Long range shooting usually requires your better than average components if you want to achieve some modicum of success.
Gas guns are not known for the best accuracy at longer ranges. It would help your understanding if you would look at the groups and distances of some of the long range competitions which feature bolt action rifles then compare those to any of the similar for gas guns. You'll find that the gas guns lack the precision and accuracy of a properly built bolt action rifle. But that doesn't mean you can't use a gas gun for some of the long range shooting, just understand the limits.
There are quite a few variables for achieving accuracy when assembling an AR platform. It's not the erector set simplicity that many try to convince you. There are few rifle builders who actually understand this and can back it up. Most others simply don't although they think they do... DIY builds usually fail to achieve longer range goals.
And, as noted above, an excellent trigger can be the make or break component. Most AR triggers are not worth using on a long range rifle but the best triggers are insanely overpriced.
In my estimation, 600 yards for large frame AR platform is a good goal. If you're thinking of longer like 1,000 yards and out, get a bolt action rifle, it'll save you money and aggravation.
Enjoy the process!