So some elements that make a good archer are...
- Supporting Feats: Sharpshooter being the most important by adding damage and negating range/cover penalties. Crossbow Expert follows if you're into crossbows. Elven Accuracy is niche but could be helpful if you're shooting a lot with Advantage (from stealth, for example).
- Attacks: More attacks means more damage, especially when combined with SS. At least 11 levels of Fighter to get 3 attacks for an Attack action is very nice. Also Action Surge and similar action boosters are helpful. Xbow 2-weapon style increases rate-of-fire as well.
- Accuracy: Attacks are only effective if they actually hit. Although you'll hear comments that the -5 to hit on SS is a mild nuisance, it is a significant penalty that you'll want to shave as much as possible. Archery Fighting Style is a must and to-hit enhancements like Precision Attack, a +x magical weapon, Bless and others improve your ability to put damage on target. Shooting with Advantage also helps, so good stealth capabilities and other situations that can confer that are good.
- Damage: The reason you're shooting in the first place. With high rate-of-fire the SS bonus is your bread and butter. Additional base damage from a high Dex and magical weapon bonus is good, too. Then there's bonus damage from abilities like Sneak Attack, Hex, Colossus Slayer, Hunter's Mark and the like which are always good to have, especially for Crits. Try to make sure the minimum damage from each of your shots is striking for at least 20hp. Also a magic weapon is imperative at higher level to ensure you can effect all targets.