To raise effectiveness you have to feed it around 5 tames. Parasaur, Phioma, mosschop, or anything is can grab that can take a few hits before the stalker grabs it. Levels don't really matter except for amount of health the tame has. On Gen2 I picked with Void Wyrm and put in a trap. I used double compartment trap. One for tames and other for the stalker. Start taming process using blood packs, feed tames, and then finish taming with blood packs.