This might not come as a surprise that most of us started by picking a game engine or a framework to build games. It is easy for a newcomer to be drowned by the sheer marketing of some of the commercial game engines out there, which you should be aware of. It is even easier to give you an advice to just pick any of them and it won't matter. It does!
Here I just want to mention some of the risks you are about to take and hope that this will help you think more critically.
There are more than a few hundred game engines out there and each of them does one thing best; making games. You might be right if you think that choosing any one of them is fine, but in reality they can shape how you approach games development and some will even deter you from starting out. Mind you, perseverance is an important factor in games development.
All game engines have limitations, pros and cons. Many factors can go into deciding one but sometimes, all it matters is you could make a complete game with it.
Assets are a blessing and a curse. Let's talk about the benefits of assets first. At first you would definitely need a template of some sort to try and clone a simple existing game.
If you are already thinking of downloading some templates of clone games, good for you! But try harder.
Assets are mostly meant to accompany a game developer in their journey to mastery, be it getting code examples, art assets, sound assets or game engine extensions. It should never be considered the pinnacle of success.
Take tutorials for example. You might not be using your creative juices and experiment with different approaches. It takes efforts to follow a tutorial and it is not worthwhile if you would just skim through a 30 hour long tutorial just for the sake of completing one off your checklist.
Give yourself a chance to play around with the variables and tweak to your liking!
It is always important to avoid the urge of publishing something free or charged to the public with assets you can obtain online, even if it does not violate any copyrights. Keep it to yourself.
The main reasons are because of the concerns with asset flips around the internet. These are the games that were put together with assets that were bought or downloaded. Dead simple to make and floods the marketplace with ill intentions to quick profit off by selling at less than a fraction of a dollar. This is exploitation at best. It does not promise good success, stains your reputation and it affects the indie games industry.
As a game developer, have pride in your artistic work.
A game's monetisation mostly depends on the tools it is used to build and definitely some of these tools can be too taxing.