If you want amazing damage in LD, get Gran Faust, two pentas, and a Skolver set.
Fixed that for ya.

If you're recon, your damage is luck, based on the number of aggressive strikers on your team. You'll have low damage because they will find enemies and hit them while you're busy walking around. They're back in the fight after deaths before you can pass the heal pads.

That aside, your damage will go up depending on:
1) How often you run into 2+ people at the same time (simply, running into 1 person at a time will not get you high damage).
2) How often and consistently you land your shots. Your enemies have the same health whether you have max damage or not. Damage only changes how many shots it takes to get there (and of course, using less shots to kill might mean surviving longer).

As far as gun choices go:
- Cryo driver line freezes people, allowing for near-guaranteed kills in 1v1 or letting you survive a 1v3
- Volt driver line shocks people, dismantling invincibility frames, letting you instakill people, if you're fast/powerful enough. Great for teammates or max ASI gunners.
- Firo driver line sets people on fire, which is good for slower kills (guardian) or times when you're unable to consistently hit targets or die a lot.
- Prisma/Shadow are your damaging guns (they're kind of like Acheron as far as guns go), but if you're not recon, you have to choose guns that counter your target's armor.
- Blaster line has decent range (just about the same as polaris), way faster bullets, and more range than alchemers by about 1.5 tiles. It's a great utility gun, and for recon, is the best dueling gun you have since deathmark makes it way too amazing.
- Magnus line is terrible for recon, don't use it. It's maybe ok for striker. It's like using a really long toothpick that has the delay of a fov when you slash. It sucks.

As far as hitting people goes:
- Learn to lead shoot - distrust what you see because what you see is probably going to be 50-100ms behind what the server sees. You will often need to 'miss' ahead in your screen to 'hit' on the server, and hitting on the server is what really matters. For normal walking speed, this can mean 'missing' 1-2 tiles ahead. For strikers dashing, this can mean 3-5 tiles (!!) of 'missing' ahead. It's terrible. Quit using guns.
- Recognize patterns: When leadshooting on reflex fails, you can only rely on prediction. In a gun fight, you can predict where a striker gunner will stop to shoot and hit it before your target sits there. If you can aggravate strikers with guns enough, they'll have to approach, and when you know they'll do that, you can try to cut off their approach or shoot where they'll stop to attack.

TL;DR:

If you want amazing damage in LD, use striker, swords, two pentas, and a max damage set.

The issue with magnus is that it forces you to stand still. For a weapon with so little width and no knockback, you'll need a lot of speed, attack consistency, and accuracy to keep someone from reaching and hitting you, that or godly footwork. And that only applies to that one person. If you're dealing with multiple people, you WILL take hits from at least one other person after 2 shots. Recon's number one weakness is its mobility, so you need to be able to move and get back into cloak as soon as possible.

The charge can counter a polaris bullet from outside its range by about 1 tile, which is pretty awesome if you're firing upwards against people shooting down (see: Reactor). But that kind of use is situational at best. Striker can kind of kite with it, since boost lets you maintain or gain distance really easily.

I'm not sure about levels of damage bonus and guns (as far as I'm concerned, you need to fight for every hit with caution as long as they can move - any underestimation can be your death), but for most swords, every 2 levels reduces number of hits by 1.

IMO, your best movement options open up from ASI, so ASI armor (justifier/nameless) will keep you at a place where you can get your aim and movement quick and polished. When you become more of an "endgame" player (ex: get ASI UVs), you can switch to shadowsun or chaos, using UVs make up for the ASI.

Generally, the most important thing with guns is consistency. Consistent aim and gameplay can prevent melee people from hitting you altogether, even if it does take more shots to do. If you can get good avoiding hits with just ASI, then you can add damage trinkets to kill faster.