A quick way to get this one.
Start a new game.
Select challenge - The invicibles- Easy difficulty
Choose the Icelandic league, you only need the top 2 divisions.
Take over IBV.
Sim the games (save before each game incase you lose and reload if so).
I won 3 games in a row and that was enough to clinch promotion, where iceland only has 2 leagues, it counts as bottom to top and unlocks the achievement. You can also go on to finish the challenge and stay undefarted and unlock the achievement for the invicibles as well.
For some reason, the you're up achievement for winning promotion didn't unlock for me.