Okay i got a JG BAR10 scope package, an echo1 harris bipod, 2 extra mags, and a bag of .25 airsoft elite bbs from ASGI. i love the gun to death even though i have only used it once. I used it at a friend's b-day last saturday and used nothing but the afforementioned items against several veterans of airsoft playing 5 HITS to the out with only one life and to make matters worse MY SCOPE WAS NOT ZEROED AT ALL!!! long story short i got tore up. but enough about that; i want to know if i should hang onto the .25 with the stock bar10 or move up to .28 or .3s? also what should i get in order including anything i could need like a ghillie suit, sidearm, holster, and upgrades (on the upgrades what order do i get the pieces in and how much does each cost: i plan on getting a tightbore first and want to know what diameter to get). also im having trble getting the scope zeroed i know where it is shooting: LOW AND TO THE RIGHT, but which direction do u adjust knobs? i tried turning it UP and LEFT but that did nothing and seemed to make it worse but when i turned knobs towards the shot grouping it seemed to get closer to the bullseye! IT IS IMPORTANT THAT I FIND OUT AND GET IT ZEROED ASAP BECAUSE I HAVE ANOTHER GAME WITH THOSE GUYS IN THE NEXT TWO WEEKS AND ACCURACY DOES MATTER ESPECIALLY WITH NO SIDEARM. oh yeah i only have a place to shoot my bar10 up to 100ft and was wondering at range i need to zero it: either 100, 150 or 200 i want to have it zeroed at the maximum accurate range. my friend has his zeroed and said the bar10 won't even shoot 100ft (is that true i really don't know). thx i'm still a noob, but i'm getting field experience slowly!

Where to start...

Alright, first off, a stock BAR-10 can't use much more than a .25~.28 range BB anyway, since the stock spring isn't going to push enough FPS for heavier BBs.
Sighting the scope is something you can just google, or go do with trial and error. Mounting the scope correctly will help IMMENSELY in fixing your left/right shot deviations, and
sighting your scope in a windless area will help too.

Another thing to realize about airsoft BBs is that they don't follow a ballistic trajectory out of the barrel. Due to the hop-up's backspin, the BBs actually float slightly up at first and gradually fall back down as they lose momentum. Somewhat like an elongated sine wave coming out of the barrel.
So sighting is generally done where the BB's flattest flight path is.