Please explain how to protect me in this situation from scythe?
How many thousands of metal should I spend to defeat this imbalance of an invisible creature?

On this map where spiders, planes and cloaks are king, I'm pretty sure you can muster any one of: fleas, glaives, swifts after you scout cloaks.

You know scythes are coming, and you also know the locations that they will be going to. Use your options.

Also - if you are not engineer and you see cloaks (or rovers), do yourself a favour and upgrade machine gun. I don't care about your stealthed lightning trollcom fantasy endgame; the situation you are in calls for machine gun. If you're still feeling "exotic", get the EMP stunner d attack.

If you think there will be a lot of Scythe you can put Lotus on spires to keep the out of Scythe range.