[Secrets]

Not bad at all for your first game attempt; I'd recommend continuing other projects once it is completed (if it's something that makes you happy - DON'T ever get roped into this for a living if it's something you aren't passionate about). You'll want to try and make other games and learn from your feedback. Being in game development as a programmer now, I can't offer much from the design perspective, but...
Unfortunately, in the AAA games world, designers are underpaid and short of creating a hit product in the past and bringing that talent to another studio, you probably won't find work short of working for yourself. So if you REALLY want to design your own games, you're gonna have to do everything. Here's some tips:

The game needs to be object-oriented. You appear to be using yoyogames.com's GameMaker software. I am not familiar with this program however I can tell that it's meant to be transparent to the end user using the product. This severely limits your potential for object-oriented programming. An engine like Unity will teach you the basics of OOP and inheritance via C-style languages so you can eventually transfer your work into the 3D or 2D-in-3D worldspace and beyond.

Imagine if you could have a base player object, but instead of equipping it with weapons that you drag and drop and cannot change the functionality of, each weapon would be another class object that you'd attach to the base object itself in some way (in laymans terms).

This is all possible in Unity's Gameobject and UE4's Blueprints. It is better to learn those concepts early and not getting spoiled by someone doing all of that work for you.

I recommend reading up on Unity and abandoning the engine you are using now. It will teach you more in the long run. Even if you use Unity's asset store, it will teach you more about programming than any other game engine while still retaining the 'fun factor' of indie design principles.

If I was making a new 2D Game, Unity is primed to spoil you without forcing you to take shortcuts due to technical limitations. If you want to delve into the rendering engine, though, you should definitely use Unreal 4 instead.

Hope that helps, and good luck.