Interesting, Very Interesting. My First 3D game was based off a 1980s space/Planet Exploration Game. The Game used pixel plotting to simulate 3D Graphics. Everything was an outline of what it was supposed to represent. Mountains, Buildings Bridges, Spacecraft were all pixel plotted outlines. The game had 3 difficulty levels from easy ( Strictly Exploration) to Very Difficult ( High Frequency of attacking enemies ). There was supposed to be collision detection so that you could not fly through objects, which did not work.
So as a Beginner's First 3D Project The game was Simple. The Game had only 2 spacecraft, yours and the enemy with geosync Space Station. I began by building My version of these spacecraft with the 3D modeling software and as they were completed, would animate flight in my code. The terrain was also kept simple, Sticking to the original game premise, Only expanding it by adding different Models.
Basically, In my opinion, as a complete first 3D Game project. Keeping it simple, with a game outline that is equally simple, but that would keep a player's interest would be essential. In the original game, the exploration required you to discover space artifacts that gave clues on how to secure the planet's safety from enemy attacks. I accomplished this by randomly placing these items around the Terrain at the beginning of a campaign.
Again - Keeping it simple, with something as the programmer, you are interested in