==Stone==
The denser the better. That's why rocks > concrete > cinder blocks & bricks.
Heavy black basal rocks and black tourmaline work best as they have a high iron content. Check out the YouTube video called "Does Black Tourmaline Protect Against EMF's? | EMF Protector"
If you can find them for bulk and cheap, you can fill them in a gabion fence for some major protection while you sleep.
==Metal==
Basically, if it can conduct electricity well it is good enough to block microwaves. Copper and silver is best. Next is iron. Aluminium is cheap but still a good material.
Aluminium mesh screens work great even with the holes for low frequency wavelengths like microwaves. See "Shielding RF Radiation with Aluminum Screening" by thisirradiatedlife. Build a Faraday cage. See "Sleep Inside A Faraday Cage" by PrognatusSeptem on YouTube for a good example.
Spend about $20 on stainless steel wire/rope of 300+ feet on Amazon and wrap it around your house. This will act as a big antenna for the microwaves.
==Water==
These WiFi signals effect water molecules. Since we're mostly water, that's why it can easily pass through other materials with a lower moisture content. So use water as shield to absorb it before it gets to you.
Buy cheap pool rafts and fill it with water at Walmart. They should be $5-7 each. Fill them with water and build a fort with them.
==Summary==
Remember, stone needs to be dense for it to work. Other than that, try to combine from the three categories above and the thicker the better.