First off I want to say don't be intimidated by arrays - they are in essence spreadsheets where you can store and manipulate data. One important feature is that they can grow and shrink as you need them, unlike variables, of which you have a fixed amount defined ahead of time. Very useful.
Basically, your goal is to get teams randomly from a list without repeating. I would use two arrays - the first array contains all your teams and data, the second array starts off empty but when we need to we can move the teams in the desired order to the second array (so that the first two slots play each other, next two, ect.). After the data is processed, they can be moved back to the original array in the correct order as well.
Here is the commented example - https://www.dropbox.com/s/uu31uxt73zkfx ... .capx?dl=0
I made heavy use of loopindex, let me know if you have any questions.
This technique is very similar to shuffling a deck of cards. Imagine you have a "deck" of 52 teams (or 4 in your case), and after you shuffle you draw the top two teams, play them against each other, and then keep repeating until you run out of cards. Sorting them back into the original order is optional.
If you don't mind using plugins, here is a plugin that might be useful - plugin-smart-random_t163624