I want to build around Lightning Arrow (shadow)

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Well I'm not going to recommend a specific build, but using lightning arrow to clear trash mobs generally goes like this:
1. Get pierce nodes east of the shadow.
2. Use LA, pierce gem, GMP, and whatever supports give the most damage.
3. Get crit, accuracy(unless lioneye's glare) and some combination of phys, elemental, and projectile damage(depends on your bow) nodes.
4. Try to path near life clusters so you can have enough life(170%+). Try to get at least some secondary defenses. Evasion + acro is great for softcore to 90. Evasion + armour hybrids are pretty solid too but harder to get set up from a shadow starting position.

As far as choice of bows go. Lioneye's glare and voltaxic rift are both dirt cheap and very effective. With lioneye's you'd build around phys, with voltaxic you'd build around elemental/projectile. I think a good harbinger is what people usually use for true endgame damage but I've never tried one.

You need a different gem for single target. I'd recommend barrage or blast rain. If this is for legacy league double dipping poison by stacking projectile damage on a physical bow should be a good option for single target.

Every bow shadow I've ever made was an assassin. I don't see much value in the other classes for bows.