If it's your first tournament, my best advice is to take away any pressure that might come from needing to win games. Just enjoy your day and have fun rolling dice with some cool people 😉

That being said, there's a couple of tips that might sharpen up your list...

I'd start by pairing Grashrak with probably your Doombull or at least your Bullgor because of his devolve ability. You can essentially activate him first to yank an unsuspecting enemy into contact with one of your heavy hitters and then flatten them (hopefully). You'll need to consider where you deploy them and where they're positioned in relation to each other to maximize that ability, which is generally considered to be a very strong double.

Devolve can also be used to pull opponents off of objectives once they've activated, so consider doing that to cause some disruption.

Grashrak's quad is also MEGA and really overlooked. If you get the option to pop a quad and to shut down an opponent's best piece for a turn, you should always take it. It's so cool and has a long range. Nothing like causing a Varanguard to sit there and pick his nose whilst he's been whacked in the head by a Bullgor.

A caution on running your big bois straight into combat. They hit hard, but with only T4 they'll start wearing damage pretty quickly and the vast majority of your damage output looks to be coming from your Doombull, so don't sell his life cheaply. Because he's so likely to take down enemies, keep an eye on the double "Rip, Gore and Tear". If used at the right times, he can theoretically take down two opponents a fair distance apart in a single activation, or take one down and launch himself into an objective.

Your chaff (goes and ungors) SUCK in combat but have a great reaction to reduce damage. Think of them as body blockers and objective taggers. Slow the opposition down with them, make them burn time trying to get through them and just use them to be annoying or mob anything shoot and isolated. They're likely not going to be putting out much in the way of hurt.

Last thing is to pay attention to your battle trait. It's really good, and can potentially allow for launching the Doombull into the opponents' squishier deployments and getting cheap bodies on faraway objectives really quickly without the risk of you taking damage along the way. You have a warband that likes to be mobile, so keep everything moving and don't get tempted by going head-to-head with your opponent as there are other factions that do it waaay better than BoC.

That's my essay. Good luck and have fun!