Hey! This looks interesting. Indeed, you do need to work on fundamentals--and interestingly; you can draw well from observation. This means that you are mainly lacking the ability to think in 3D and project your designs as such. This is seen by your repeated choice to portray things in a ancient Egyptian way.
As for the focus: Pushing the designs.
I think you first need to work in bigger formats. These seem like first drafts, perhaps first version of the designs ever. I recommend you to go over each one of them properly.
This is usually done in the game business. Instead of directly drawing the designs from imagination and keep the first designs everytime; they go through a conceptual process.
So in this case, each one of your units, or creations, can be described by either story, or tropes. Either way, you can simplify things by dedicating a page for each of the designs. So for instance, your first spider-bot. Take an A4 piece of paper, and draw it differently until you have at least 5 different designs of it. These are supposed to be rough, and you want to explore shapes and negative shapes during this process. Don't spend too much time on this, but play with the shapes, and create good shape language, and something you are satisfied with. After the five drafts, pick one of them, and take another A4 page. Try to define the design properly, where it is visible and comprehensible.
When you are at this stage, you want to take from the intended purpose of the thing you are creating. So, we all have things in mind when creating things, and I am sure that you had some thoughts about the spider-bot, before you drew it down. So, what is it? Is it a robot spider? is it supposed to be grim? scary? fierce? define the creature, and do look at reference eventually. If your spider is supposed to be steam punky, look at that style, and take from those designs to forge your own.
Now, it seems that you are mainly lacking clarity in your designs. You mainly have the shapes, but there are things lacking. One thing that we never want, is for someone to look at these, and question what is going on. It is important to make things obvious and clear at first glance. So, as for what you are mainly lacking; I would say definition, in the sense of meaning and thoughts behind the designs.
For example, the tank. It seems like a normal tank, but is it? Does it have the long wheel-like things that tanks have? or is it more like a turret, stationed at one spot? How does it stand, how does it fire? Is it a tank, or something that fires many times, very quickly? Is the style realistic, and is it inspired by a real life machine, or is it sci-fi? in which case, you can research for reference either way.
Now, this all might seem a bit daunting, and I'm going to hold off a bit. Just to re-organize and simplify what you need; Clarity. Think about your designs, what they can do, and why they can do it. Functionalism makes for very interesting visual aesthetics, and then on top of that, add designs based on things that it is actually based on, using reference.
Anyway, I hope this doesn't seem scary! I really like your idea, and of course, most of what I've written is probably for people who are already working in studios! So, you don't have to put too much effort into each individual asset, but I put all this information out here, so you can choose what to prioritize, so you can properly flesh out one of your designs. 
Anyway, keep up!
