There is not much to specify for the question, its really simple: Which title is the first game you have purchased on Steam? Was it a good decision? How much did you pay? When was it and what device? You don’t have to answer all questions, this is just a fun discussion to have.
You can check your history: https://store.steampowered.com/account/history/ Edit: Some in the comments pointed out that the purchase history doesn’t go back all to the beginnings of Steam. So if you purchased something earlier, it won’t be listed on your account.
(I reply with my game too.)


The first game I ever paid for, but did not directly purchase, was Garry’s Mod in 2011 or 2012 after UndeadPatch stopped working. I didn’t have a bank account, so I paid a classmate in cash to gift it to me. Considering that I first learned programming through Wiremod’s Expression 2 chip (basically a virtual ESP32), leading directly to my computer science studies and my current job as a sysadmin, I’d say it was $10 well spent.
My first purchase on Steam was “The Classic”, a sniper rifle in TF2, just to remove my account’s F2P trading restriction.
Then I got a whole bunch of games through Humble Bundle’s subscription. The first one was December of 2018, specifically for MGSV.
The first game I ever actually bought, actually on Steam, was Slay The Spire.