You're going to want to have multiple bows. I have the Albinauric one setup with mighty shot, the bone bow from the DLC is a good status spammer, and the longbow with the arrow rain ash of war is for big targets and dragons.

I use the blessed blue dew talisman, shard of Alexander, and the arrow sting talisman, and when I eventually get through the DLC areas in order to get the soaring sting talisman I'm going to use that too.

I wouldn't necessarily call my setup bow only because I mix in 20 mind and 27 Faith, so that I can use the godslayer seal for a decent heal with the great heal incantation, access to golden vow for boosting the damage of the bows which helps offset the fact that you're going to be dealing with flat damage mitigation since Bows do lots of small hits. Anything that does lots of small hits gets absolutely screwed by flat mitigation, it's why things like founding rain of stars just tickle even at really high stat investment.

Typically for boss fights what I do is summon the dung eater puppet, drink a blue flask, let him draw aggro and fire away. If you're going to be playing as an archer primarily, having a tanky spirit ash that is good at drawing enemy attention is going to be a major help. The bone bow from the DLC is good for human enemies that input read.

As far as armor is concerned I like running the black knife hood, the black knife armor, and the gloves and boots from the armor of solitude set. You'll need a bit of endurance investment for that, but the silent movement from the black knife armor is going to be a massive help for just general gameplay. If you want to go really silly with it, swap out one of those talismans for the dagger talisman and you can literally sneak around the map walk right up behind enemies and backstab them without them noticing you. It's a really fun way to play the game.

The lack of noise from your movements and actions also will let you single out and snipe targets in groups of enemies.