@Gairyuki789
Hey don't worry man. This place is where silly questions are meant to be asked ;)
In all honesty, the item choice is heavily dependent on:
a.) What your Hydreigon is trying to accomplish
b.) What your team struggles with
Dragon Gem should be used when you need to boost up that Uber-Strong Draco Meteor to even higher levels. Use Dragon Gem if your Hydreigon is trying to lure something in. Let's say Pokemon X is able to take a non-Gem Draco and respond. You need to fix this and by giving it a Dragon Gem, Pokemon X could switch in only to be demolished.
White Herb is really useful for those icky I-could-get-a-2HKO-and-I-can't-switch-out.
Let's say Draco Meteor on Pokemon Y is a 3HKO. You need to 2HKO it and either KO it or heavily damage it. You also cannot afford to lose momentum. This is where White Herb would be real handy. Note that this should be used sparingly and cautiously. You must know what Pokemon your Hydreigon attracts and see when to unleash a Draco Meteor.
Chople/Yache Berry is very dependent on what your team can't handle and what you could do once you survive. Let's say your team can't take Fighting moves. Thus you would use Chople to take a hit and KO in retaliation. This removes a Fighting Type and eliminates a threat that your team couldn't handle.
A good example is CS Terrakion vs Hydreigon. With Chople you'll take the Scarfed CC and in turn you can OHKO with Draco. If your team struggles with Terrakion, Hydreigon will act as a great lure-and-kill. The same can apply to Yache.
My Hydreigon is my team's main special attacker since Starmie functions for other things.
I read over what you've said and I do seem to have problems with fighting pokemon more than anything else with Hydreigon, so perhaps using a Chopple Berry is the best idea...but does the berry counter the CC enough?