Alright... So feel free to place your own at your leisure. But the best weapon to get and upgrade (in my own opinion) would be the Javelin. It has the ability to pretty much one shot everything currently in the game. The Equipment I used allowed me to end my play through with every item fully upgraded and over 110000 lux.

So to start with the Javelin has damage procs and energy efficiency upgrades like any other weapon. It also has two distinctive abilities. The first one being my favorite which is a really good increase to damage via sneak attack/backstab. This is further enhanced by an augment that increases the afor mentioned by 50%. (I think that is what is was)

The second ability is a fully charged bolt (Hold LB down for increased damage) will always stun. For anyone having issues with enforcers, or any other enemy this is a game changer. Not only can you get them into a stun lock, but you also get the increased damage at the start through a sneak attack.

Things to note: The Javelin is really easy to spam, so it is highly recommended to get equipment that helps to boost your energy.

I used in my last play-through the largest energy upgrade (300 to start) as well as the support that gives you a passive boost to your energy gain. This one in particular is almost a necessity. Once fully upgraded its almost completely unneeded to use any Energy Cells. An example is that while firing I was visibly seeing my ammunition counter rise as I was engaging enemies.

Other than the passive regen for energy your other supports really don't matter. Choose what you like the best, I didn't play around with any of the other energy increasing supports, so explore and have fun.

Now then, onto the armor. I really haven't seen any difference with armor. I don't know if it hasn't been implemented but in your status screen, the only thing that changes is how loud your footsteps are. So I would suggest going with armor that has + to silencing. Damage reduction wise, changing from armor to no armor seems to have no effect on how much damage your character takes.

And finally (Mostly because I am running out of things to type endlessly about...) how to most easily upgrade your weapons...

Before the recent updates, it was a slight pain to upgrade your weapons or get better versions of armor, shields and what have you.
Now though.. It is a bit too easy. I'm sure by now you have all noticed that you can craft things. Within the first hour or so it is more of a convenience to harvest resources from the environment. So make a temporary stronghold or something and once again enter your engineering menu. (c or the tab in your inventory) From here look to the top and click on one of the items there. An example being a Vanishing Shield. For each 'Tier' you will have to have parts corresponding to the locked recipes. So to upgrade from tier 2 - 3 you would have to have already made a F.A.B. and then make a L.A.B.. After that just make the needed supplies and then click on the Vanishing Shield again (You have to back out of the recipe and click on it again or it won't currently work) and upgrade your item.

I say in the first hour or so because after that you'll have unloaded your unwanted items enough times into Recycler for Lux that you have enough to splurge. After you are more comfortable with how much you have in your wallet, breaking down weapons and junk is a lot faster and time efficient.

Speaking of the Recycler and Lux. Due to the large amount of cash inflow with the introduction of the Recycler, Upgrade Cells are no longer something you can only look at and drool over. But something that you run around looking through each kiosk buying them up as soon as you find them. And once you have started getting your gear more upgraded you'll find that killing Widows, Reavers and seekers become an easy process. That also comes with the added bonus of having more frequent Upgrade Cell drops until you are fully upgraded on your gear.

Anyways, Imma stop taking from your life if you've gotten to this point. I hope you have gleaned some new information out of this and it hasn't been a waste of your time. If anyone would like to suggest things or express their views feel free to do so in the comments.

Thanks

*Will add the items I had equipped when I run another play-through as well as make some variations to the guide. Maybe some pictures if I feel like it too.*

Alright, so these are the two items I'd highly suggest. They allow you to not only regen quite quickly but also maintain more energy as you are attacking enemies.