Help me improve my weapon sprites

[WorldEater]

So for years now I've really wanted to be able to make sprites from 3D renders. I really like the look of sprites from games like Supplice and Ion Maiden, and obviously Doom, and this style is exactly what I want to achieve.

The problem is that I have never been very good at drawing or understanding anything about creating visual art. My lack of drawing skill is one of the reasons I want to go with renders. I'm a 28 year old stay at home dad with two toddlers so I don't really get much time to learn new things like drawing. So what I'm looking for are any tutorials out there that could help me with what I'm doing, even drawing tutorials that will specifically help me get better at drawing guns in first person perspective so that I'm not spending a ton of time learning things that won't really help me very much. I'd like to be able to create a road map of all the topics I need to learn and everything I need to practice.

Things I have done but suck at:
-I have been able to make (ugly) sprites in Blender by rendering models but I've been told my lighting set ups are not good. I have no idea how to create a lighting setup that looks good. I always use a sun but have experimented with adding point lights around the model. Nothing seems to help.
-I can index sprites in Gimp to give my sprites a palleted look. One thing I don't really understand is choosing colors for a palette and how to make sprites look good with limited colors. How do I know what colors I should pick?
-I have read Eriance's old tutorial for making centered weapon sprites, but I seem to have an issue understanding the process he uses. I remember one point perspective from school and I'm not too bad at making a box in perspective on paper, but when it comes to making a sprite I can't get any further than that. After making a box I really have no clue what to do next. I suppose I should try to design the side view of the weapon and then sprite it while using that as a reference but I don't know how to be creative when it comes to designing things like that. How do you guys create concepts for new weapons?

I have talked with Supplice's/Ion Maiden's main artist about how he does his sprites and he told me about using multipass in Adobe After Effects. I can't afford that right now, but I found out today that Blender apparently has something like that? I don't understand how to use it though. From what he told me he seems to make multiple passes and combines them into one but I'm unsure how this process works in Blender.

In a perfect world it'd be nice if someone out there could make a video tutorial about this topic covering everything from setting up the model to hand-painting the result. Nash used to at least have a video about making a sprite from a photo and using PS to match the colors but he has since deleted it and I haven't been able to find anything close to it.

Lastly, here are some sprites I've made to show you what I'm capable of so far. I've been told my main problem is lighting.

Please help me...I've been trying to do this forever but I'm just really stupid or something and need someone to point me in the right direction.