I make up a list of ~$300 worth of stuff for the year, and as I get that list marked off, I +/- what I spent on it vs estimate, then use the gap to treat myself near the end of the year, since I find I can snag some good deals to round off the year as people are selling their old stuff to buy new things .
I really like this idea! I find myself in the same position most of the time. Not a completionist, just looking to capture the games I loved, and the ones I thought I might.
I cap at $50 for the essentials, LOZ:LTTP, Super Metroid. Still looking for FFII & III under $50, but I have made some friends I think I can work with.
I don't trade so there's that.
I don't do much trading myself either, but a good deal can always break that rule.
I typically function in my own little bundle economy involving bundle purchases and reselling:
Let's say that there is someone selling a console that is bundled with 5-10 games. Now, I already own that console, and most of the games, but there is value here.
An example I've had in the past was: A SNES with Donkey Kong Country, Mega Man X2 and The Seventh Saga. The ask here was about ~$120. That's the value of X2 alone. So, I snatched up the whole thing. Dusted off X2 and Seventh Saga for myself and resold the console and DKC for ~$70. So, I'm only down $50, got X2 and Seventh Saga. A $70 is a more than reasonable price for a SNES and game in this area.