Can I use Acceptable Losses even if I don't have a Gear?

Yes, you can use Acceptable Losses even if you do not control any gear, as long as your opponent does.

According to RiftJudge FAQ #4344 and #9554, Acceptable Losses does not target. Instead, at the time of resolution, each player who controls gear will choose one to kill. If you control no gear when the spell resolves, the instruction to kill a gear for your side simply cannot be performed and is ignored (see also RiftJudge FAQ #10178).