Hello, I am sharing the capx of the minimap that I needed to my game in the last JAM.
This 'capx' was made in a basic way with the help in the forum (thank you very much for your help Guizmus).
To a very large layout, according Guizmus, "the map size isn't the problem. The problem is the number of points on the map and the trigger "on every tick". You'll make it faster by updating the map every 0.1 second for example, or 0.2. Also, you could hide the points of the enemies whose icons are outside of the map if you have a big layout. Optimization should come later in your game, when it starts to be a problem, or when you are shipping it to another support than PC. "
And for more help, read the recommendations of this tutorial http://www.scirra.com/tutorials/598/o
I hope they help in your project.