Puah. thats a hard question because there are so many tools out there that are really different.
I short you cna use nearly every 3d graphics tool to achiev what you want.
so the hard part is to find the right tool for you.
My personal prefarence is blender. I started with cinema 4d and maya. But I never liked them to much. Blender was the tool i really started to understand 3D. So it will likly be a journey.
Blender has a huge community and incredible amoutn of tutorials.
While some dont like blenders UI its super fast to wrk with and nearly all tools have a drawback of some kind.
You could also have a look at 3DCoat. It's sculpting but you can also make cool hardsurface designs using it's voxel tech.
https://3dcoat.com/home/You can also use tinkerCAD or other more focsed small tools. It mostly depends on what you want. Maybe start with simple buildings and print using shapeways. Just to learn the whole process of printing.