The oldschool days of game design are over and now things are easier than ever. A game engine takes all the diferent aspects of a game like graphics, sound, ect and puts them all together for you in one place. I can only really speak for Unity but Unreal is like 80% the same as Unity.

Before we get started, if you're looking to start your own team with no experience or skills, then don't. Could you form a team? Yes but I promise you it will deteriorate. The main reason is your programmer is going to be doing 80-90% of the work. The chances of a coder who has no idea what to make and isn't willing to learn the rest of a game engine to make their own game, is so slim that it's not even worth considering. You're not going to find someone like that. There is no "I'm the idea person!". I spend maybe .001% of my time on ideas and the rest is implimentation and bug fixing. If you don't know how to make anything code-wise then you'll have no idea how long implimenting something can take. A simple idea could take 5 minutes or 5 months. If you're the team leader, you're the coder. That's just how it works.

There are tons of free stuff in the asset store, including a FPS controller that you drag and drop into your game then poof, you have FPS controllers that are highly customizable. You'd be shocked by the things that look almost AAA quality that are completely free. There is more than enough to make almost any game you can imagine without spending a dollar. Typically the more customizable something is, the more expensive it is. 

First off, if you're offput by the idea of programming, there are three solutions I have for you. They're called visual scriptors. Instead of writing long sections of code, you create a 'state'. Think of a state as a list of instructions made up of actions. When you hit a point in your programming where you go "If THIS, do THIS" you'd need to transition over to another state. It's very visual and easy to use and a lot less writing. 

1. I use Playmaker for Unity. Yes it costs 65$ but it was well worth it. It has a vast community of amazing people as well as people are able to create and upload their own actions for others to use so it's a constantly evolving add-on

2. Unity has a free visual scripter like Playmaker called Bolt and there are apparently several others I can't vouche for but give them a try. 

3. While you can also have Chat GTP generate you a C#, this isn't advised as it is known for being full of errors and doesn't really teach you anything.

As for the game engine itself, you're going to have a' scene view', which is what you see from a developer perspective,  as well as a 'game view' which is only what the player sees. Your scene is essentially your level, from a gamer perspective. You can see whats in your scene thanks to the hierarchy that shows all objects currently in use. Scripts must be attached to something, even if it's a completely blank object. Keep in mind that different engines use differnet terminology. Godot typically uses 'scene' to reffer to an asset you've made, for instance.

With Unity, you can go to their asset store, find something you like and click "add to assets". From there, you can go into Unity once you download the asset to your computer, import it and if it's an object, it's a simple as dragging and dropping from Unity's project folder into your scene. You can easily spawn objects into the world but you need to tell Unity if that object uses physics by tossing on something called a Rigidbody component. It's a component that handles all physics for that object like it's mass, any contraints( doesn't go a certain direction, can't turn a certain direction), does it use gravity, ect. Attaching components is as simple as clicking on the object and going to "Add Component" in the inspector window. It couldn't be easier. The inspector window is where you see everything related to what you clicked on. The other cool thing with that store, is it lets people sell their creations so if you're a 3D modeler, you can make something cool, toss it up and make money on every purchase!

After that we have Colliders. Those tell Unity if an object has a physical boundary or not. Unity, and most game engines, have colliders that are basic geometrical shapes or will be generated based on how an object looks (its appearance is called its 'mesh' so you'd select the 'mesh collider' from the list of components in the same place you'd add a rigidbody component). If you just want an object to be a graphic, then get rid of the collider because that's data you don't need. If you want an object to be slippery or bouncy, you'll need a Physics Material, which is something you literaly just right click in your project folder and create then change it's variables for whatever you want then drag and drop it onto the collider you want. Honestly these first bits are enough for you to put objects on a screen and watch them collide and roll. 

Your User Interface, UI/GUI, is pretty straight-forward. You make something called a canvas, and this is just like a painting canvas and you can put it in the world freely, or have it glued to your camera the player sees from. You can have multiple canvas' and even cameras with overlapping canvas'. There's a wonderful object for your UI called Raw Image which lets you pretty much put any picture you have on there. How images and texts are ordered in your hierarchy determines what is in front and so forth.

Then we got textures and honestly you can draw something in paint, save it, import it into Unity and slap it onto something. If you have Gimp or something else, you can easily use that. After you make a texture, you can choose a scale mode and move it around an object to get it just right. There are parameters you can adjust to make a texture move around on an object and scale it. A texture wraps itself around an object, whereas an image is just a flaoting image.

For animations, you can go to Mixamo.com, completely free and download both whatever animations you want and what characters to use them with. Unity has something called an Animator, which is essentially a pack of whatever anmations you put into it that you toss onto your character then you tell Unity which animations to play and when. Now animations get a bit tricky. You can have a single animation on something if you want. If you want an object to switch between multiple animations, you'll need to make an animator so you can adjust what animation transitions to where and their play speed. For instance, my animator might have an idle animation, and when I press forward, I tell my animator to transition over to a looped running animation. The issue is if you just go from an idle animation to a running one, it will be instant, so you might have a 3rd animation that's just that character going from standing to running, so it looks smoother. Some advanced stuff is IK, inverse kinematics. It tells an animation how to interact with their world. Lets's say your character is walking forward and their foot hits a rock. One of two things will happen without IK. Either your entire character will move up and over the rock, or your foot will pass through the rock. IK would tell your leg "Extend until your foot hits something, then don't go down any further until the leg retracts.

For cool effects, like explosions or lightning, you have Particle Systems. They generate particles and let me tell you, Particle System addiction is a real thing. You can spend hours just screwing with it. It's all super easy to understand settings but they let you make almost any effect you want. A PS just spawns particles. you can change the shape and way they spawn, the amount, the look and color themselves, how long they live for, what direction and even put in fields that pull/push them in a variety of ways! There's even options for colors/size over lifetime and you can even put in your own images/textures onto the particles for cool magical effects! Keep in mind that you can export things you make and import them into another project. I like to have a project I call "lab" that's just for screwing around or running experiments. If I make something cool, I can then totally export it and use it elsewhere.

Here's a link to making your first game where you just dodge objects and navigate a level. Super easy but also highly modifiable for whatever you want.