Sure, I'll suggest a few things. The thing about ranger is that the best loadouts don't only use guns, but a mix of guns, bows and rocket launchers.
Vortex Armor is the armor you want at endgame. It's stealth mechanic is ridiculously powerful. Other good armors for rangers are Shroomite, Titanium, and Crimson.
Accessories:
Wings are important.
Magic Quiver and/or Sniper Scope, they boost raw damage.
Celestial Shell, it's good for all classes.
Master Ninja Gear, dashing is useful and the black belt effect boosts survivability.
Final slot is your preference. I personally use a Worm Scarf.
For weapons, I recommend:
-S.D.M.G. It has incredibly high dps and low ammo consumption.
-Phantasm. It's gimmick is very helpful for when trying to hit enemies offscreen. It's DPS also rivals even the S.D.M.G.
-Sniper Rifle. For dealing killing blows with it's incredibly high damage and crit chance.
-Snowman Cannon. It's a homing rocket launcher, what reason do you need?
-Aerial Bane. It deals substantial chunks of damage to flying targets and rains arrows on enemies below them.
-Celebration. It's Area of Effect is massive and does high damage. Not as bad as most people give it credit for.
-Xenopopper. It's a fun little weapon that's incredibly accurate, you can do a lot of cool tricks with it too.
Weapons that can be obtained earlier:
-Daedalus Stormbow. It's incredibly powerful, but you cannot use it underground.
-Onyx Blaster. It's incredibly strong for when you can obtain it, but it's damage gets less significant as you enter lategame.
-Pulse Bow. The Daedalus's opposite. Incredibly useful underground but doesn't have high single-target damage.
Gun Ammo:
-Endless Musket Pouch. For non boss enemies.
-Crystal Bullets. They hit really, really hard, but you may have to inflict ichor on your target with a different weapon to use their full potential.
-Explosive Bullets. Good for invasions.
-Chlorophyte bullets. Good for small but fast targets like martian saucers.
Bow Ammo:
-Endless Quiver. For non boss enemies.
-Ichor Arrows. For use on high defense targets before switching to your guns.
-Holy Arrows. For their absurd damage.
-Venom Arrows. They have the highest base damage and best DoT debuff out of all arrow types.
Rocket Launcher Ammo:
-Rocket III. It's the high damage one that doesn't destroy tiles.