Treat the crit thing as gravy. Check out piercer feat as well its nice on champions.
1d6 is weak but more attacks with advantage each shot is getting close to 20% crit chance. And piercer feat allows rerolls and +2d6 damage.
Sharpshooter, crossbow expert, piercer level 4,6 8 20 dex. Whatever order you prefer.
Longow with 13 strength and swap crossbow expert tor great weapon master. Take that feat level 6 or 8.
What's better is debatable. Guts probably Battlemaster 3-6 level 10 champion. And how soon you can aquire a vicious weapon. Vicious weapon makes champion a lot better vs Battlemaster even if battlemaster has same weapon.
If elven accuracy is allowed youre an elf. Pick your favorite. If its not halfling or hunan as a champion. If you like battlemaster race doesn't matter to much just dont pick an anti combo.