Yeah timing is everything with skins. What helped me was reading through https://qnnit.com/how-can-i-make-money-through-the-csgo-marketplace/ which explains how the market actually works. Once you understand why prices move you can avoid buying at peaks. I used to impulse buy stuff too but now I watch prices for a few days before committing. Sometimes waiting even just 24 hours saves you money. Don't beat yourself up though, everyone learns this stuff the hard way at first