I got all the stuff I need for it BUT I have not tamed a single rex or spino.

I tried gamma Lystrix with about 10 level 350+ rexes and 2 friends and it was easy as. Since it was so easy, I tried beta with 1 friend and it was horrible. The baby spiders just ganged up together and they were so powerful. I recommend your base army like many strong rexes or megatheriums but add a Dino like a Yuty which can do the great buffs but also target the many baby spiders around the outside of your base army. This will make room for focusing on Lystrix and make it not drain your health. You could also have some daeodons for healing if your base army has 40k- health each. My experience was that about 70% of the damage enflicted on us was the small spiders and the rest was Lystrix. I hope this helps! - doubah.

I just went in with 2 rexes 😂😂😂

Fun fact, if you have access to cluster tributes, go to valgerou. Tame some deinonychus, pretty easy if you have 1 tribe mate and 2 pteronadons. Breed up the deinonychus for a few mutations, (optional). And take them to the bossy fight with maybe a Yuty and a deadon. The bleed will shred the broodmother, not including pack, alpha, and mate boosts. 3 in 1. Easy dub.

Kill this dude and get the engram for Tek boots!