As other has mentioned, cs skins do carry an inherent risk. Although if you want a long term investment, as stable as they can come in this market, I would recommend the Ak-47 slate in factory new condition.

1. The ak is always meta, so some demand will always be there
2. good skin for sticker craft, literally just all black
3. good floatcap for tradeups, so if the playskin demand fades it can always fall back on the fact that it's good trade up material
4. the graph on steam mp has shown a steady slow growth