Wow, I haven't heard about worming every 2-3 months. My flock hasn't been wormed and they're over 13 months old. Are you sure you need to do it, that often???
I don't think there are any required meds for backyard flocks. However, I like having a few things handy in an chicken emergency kit. General avian-style wound care, like betadine, vet-wrap, blu-kote, antibiotic cream, saline, etc.