Starts off right off the bat with a CUBE.
Tap TAB for Edit mode
Hit the number 3
Click on the TOP surface the one we will extrude now.
Hit e for Extrude
Press the number 2 key and ENTER which will indicate 2m in height since that is the default.
Move the UP and a new one with come forth.
After you have a few of them.
Now SHIFT click ALL the ...
Since the graphic is isometric, it seems you don't need a too realistic drawing. In that case, I would use Inkscape. Inkscape it not a 3D tool, it's a 2D tool. But as you'll see you can get a 3D-like result.
Inkscape is gratis and creates vector graphics that have good quality and can be exported to pixel graphics.
Create a rectangle and single click it a ...
Other than a time machine so as get a lot more time than 1 month you are going to need something that does it all for you.
I would suggest using the Godot game engine. The actual development language can be C++, C# (using Mono), GDScript or one of the community supported languages.
It is free, gratis & open source with a permissive MIT licence