I used a ton for my yard including tiered sections 2-3 high.

Rebar into the ground, ~2 per 8’ section, 2-3’ long depending on how many Timbers you’re going through.

I highly recommend headlok to fasten them together where you make a 90 degree turn, and/or throw a few in for tiered sections. They’re not cheap fasteners but are very strong and hold up well, available in multiple lengths.