Similar to the herobrine mod. I wish for the player to build a totem, that will then spawn structures around the map.

I'll try to explain well. You need to have a good understanding of procedure because their is a lot of things that i don't explain, its just a base.

Step 1:

Make a block that fall like sand (try to make it invisible) . Make that this block check every ticks if there is a block beside it. If so make that your structure spawn. 

Step 2:

When the totem is created this procedure will happen: Create a loop and inside of this loop make that the block in step 1 is placed at a random X and Z position and make that the Y position is really high.

Quick explanation:

When the to totem is created the block in step 1 will spawn really high at some random position and fall into the ground. When the blocks hit the ground your structure will spawn at this position.

Sorry if its not clear and sorry for my bad english.

Hope that help!