itch.io

Well, to answer the easy question, Twine is an online tool for making text-adventure games with branching paths. The stuff I had to do to make my game work is a little complex (like the inventory, day and night cycle, etc) but other than that it's really easy to use. Twine might be a good fit for your game if it's heavily narrative-based. Here's a link if you want to check it out: https://twinery.org/ 

As far as the game-making process goes, it really depends on what you're trying to do and how you're making it. For my game, I first started by writing - a lot. Anything that came to mind, anything that might be pertinent, any snippets of dialogue or description, I wrote down and saved in a Google Doc. Then, I started incorporating that writing into Twine itself, starting from the beginning and moving outward. It helped immensely to have access to a guide and the documentation; no matter what game engine you use, always find the documentation so you know what can be done easily and what requires more complex programming. The art was pretty simple; I used Piskel, which is also free and online, and also handles pixel animations as well. I did have an advantage because I already had knowledge of HTML, CSS, and JavaScript, and understood what they could do. That being said, it's easy enough to find simple tutorials online for those things. Twine itself is fairly simple, so you don't really need anything too complicated.

For a more complex game (e.g. in Unity or Unreal), there's always the process we used for development in my classes: prototype, vertical slice, alpha, and final. Prototype is just what it sounds like: get the basic mechanics working. It doesn't even have to be a proper level, you just have to get it playable. The vertical slice is where you get a single level completed, both in terms of art and level design; this way, you can see what works and what doesn't, and change things accordingly. The alpha is where you have all the levels done and can play through the whole thing, and can start play testing. Then you fix anything that needs fixed for the final product. Dunno if that all will help, but that's what we had to do!