If you can't teach them, force them.

Here's what you need to do riot.

Once a player hits level 9 in game and has 250 gold or more, every icon in the shop turns into a trinket upgrade button. He can't buy anything else, not even he has 10k gold until the trinket is upgraded.

Seriously. What is wrong with you people? Upgrade your FUCKING TRINKETS.

Do it rito.