How does my shop work for people who play mostly ARAM?

For the past few months, I've been playing almost entirely ARAM, so I had no idea what kind of deals I was going to get. Now that I've seen them, I'm trying to figure out the pattern behind them.

For reference, in the past three months I have only played three champions on Summoner's Rift: Fiora, Quinn, and Evelynn, with the bulk of that being Fiora. The my shop deals I got were for Fiora, Velkoz, Quinn, Singed, Camille, and Irelia.

As far as I can tell, it seems to be ignoring ARAM games entirely and just focused on Summoner's Rift games. Getting Fiora and Quinn make sense, because I've played them, and recently. I assume I didn't get an Evelynn skin because I bought one from my shop last time it was around. So the other four, I have three top laners and Velkoz. It seems like it's looking at all my Fiora games and giving me champs that other people who like Fiora play? I know a lot of Fiora players play Camille and Irelia. It can't be something to do with my ARAM games, because I have played Camille literally twice ever. But if it were looking at champions like Fiora, how did Velkoz get in there?

Does anyone else who plays mostly random game modes see any patterns in their discounts?

Side note, I am so disheartened by my discounts. All I wanted was a nice discount on a cool Fiora skin, and I was super excited for it. I got 30% off the one Fiora skin I don't want.