Kinda depends on what you're making and how much detail you want to put into the thing obviously. You might want to start on something simple first and work your way up.
Idk what you should use for blockland, someone else should answer that bc I'm lazy rn, but I took a class on using blender and that got easy to understand pretty quickly.
Well whatever program you have to use look up some tutorials on how to model simple things on that program and that'll help ya.