Peremethrin sprays on your clothes work best. DEET on exposed skin. DEET on clothes also works, but Permethrin works better.

DEET just "confuses" biting insects. Permethrin kills them on contact.

Just remember that chiggers are small enough to crawl through the weave of any clothing (tucking pant legs into boots or duct-taping sleeves and pant legs won't keep them out of your pants).