Synthesizers

Well this probably won't help you at all then, but for me my solution was to buy "the one" instrument that I most enjoyed. Not that you can necessarily guarantee to know ahead of time which one that is. In my case I got a Waldorf Iridium, and that killed my GAS for synths. There's just something about that synth for me that feels "just right" but also deep enough to not lock itself into a corner. Now every time I hear a new synth demo, I think, "That's a cool idea! I bet I could get close to that sound with the Iridium." And instead of thinking about buying something new, I instead use what I have to accomplish something similar. Or more likely, I start with imitating, but end up going into a different creative direction that I preferred anyway.

A similar piece of gear in my guitar arsenal is the Empress Zoia. Instead of getting GAS over new pedals, I instead hear the cool sounds and immediately start thinking about how I could replicate it with the Zoia. No need to buy a new pedal. Multi-FX pedals can be this way too -- I hear similar experiences for owners of the Zoom MS-70CDR.

So partially its finding something that you mesh with personally, which no one but you can figure out, but it is also partially being sure it isn't something that is too niche into a specific sound but instead an instrument or module that is flexible enough to be used for multiple purposes.

Anyway that's been my experience. 'course my noobish opinion isn't worth much.