how many tarps do I need?

Completely depends on what type of loads you're doing. 8 ft drops for lumber and everything else is fine, just more work. I've got 8s and 5s to cover everything, but managed just fine when I only had room for 8s. Even on flat on the deck loads. For that you'd need 8s with grommets at the very top as some done have that.

 

Two of each of the if you plan on taking lumber or any taller items, 8s alone if you want to save money while not cutting out any loads, and you don't mind the work.

 

More bungees. Easy to use 50 @ 21” on a single tarp.

 

Bungees are cheap insurance. Buy 100, minimum. Buy an extra box and keep in the truck with you.

 

Use your brain. Is your trailer 36 feet long? You should have enough to cover your entire trailer length plus some overlap, and you'll want a tongue piece to cover the end. Look up lumber tarps. Typically 24x26+8x8 flap.

 

Minimum 150 21 inch bungees