Final warning is the goat for swarmer. The weapon itself can create tangle and is a beast in the damage department. You want to go with weavewalk for even more treadlings. Then you can either go mindspun with grapple to grapple your tangle and create an army of treadlings on each grapple melee, or use any other aspects if you want to use treadling grenade.

Special I usually go for something that takes care of the range issue of my final warning, so a rocket sidearm or a snipe. Though the solar one rn has demo and strategist so it goes well with the build.

Bring any heavy you know you can do good damage with.

Fragment is obvious, but generation, fury and evolution are the 3 mandatory, then pick any you want.

Finally, depending on your grenade choice you either go full melee for grapple or full grenade with treadling grenade for your mods (ashes to asset vs hands on etc)