(For once) DnD requires you to do none of that.
If you don't have the time to have fun doing it: Don't do it.

The whole cardboard hexagons, map, thing seems really overkill to me though. If you want to build some acceptable sized landscape you're going to need loads of them.
I was never a big fan of things like Dwarven Forge, too. It's just too much hassle to set up, etc.

Though I don't like preparing anything anymore, since I stopped GMing DnD. Players will ruin your preparation, and go somewhere you completely did not expect, as the OP already mentioned.