I know only what I've read about here on BYC and some online searching. I'm not a vet, but I wanted to have some things on hand in case my birds have a problem. Here is the kit I currently have including what problem each item is good for (with pertinant links). Hope other newbie bird owners find this helpful, and please correct me if I've listed something incorrectly or left out something important.
I got all of this at my local feed store or drug store (CVS, Walgreens, etc.)
Duramycin Tetracycline for chronic respiratory disease:
Ivomec for mites:
Sav_A-Chick Electrolyte and vitamin supplement for stress/dehydration:
http://www.brittonclouse.com/chickenrunrescue/CARING FOR A SICK OR INJ 9_08.pdf
General Lube for prolapse: https://www.backyardchickens.com/forum/viewtopic.php?id=26390&p=1
Wazine for intestinal worms (do this every 6 months and don't eat eggs for 10 days after treatment)
Blue Kote for bacterial/fungus infection and to cover any open wound so other chickens won't peck the sore (I bought the hand pump kind - not aerosol - so the poor chick doesn't get a blast of air)
Kit with exacto knife and tweezers for bumblefoot or crop surgery:
Benadryl in case of snake bite:
Flashlight for inspection of problem.
Neosporin (WITHOUT pain relief because that is toxic to birds) for open wounds.
Gauze, waterproof tape, first aid wrap that sticks to itself to cover wounds (if deep puncture or after surgery)
Hydrogen Peroxide / Rubbing alcohol to disinfect an wound.
Gloves to keep you and the bird from spreading germs.
Syringe (in case you need to give liquid or medicine you can use just the syringe to squirt it into their mouth and measure the dosage).
Needles (I got the smallest they had at 22Gauge).
Epsom salt for swelling tissues (use in bath)
Apple cider for worm prevention and slow algae growth in water container:
Preparation H for swelling tissues (use for prolapse)
Thread and needle (if you perform surgery...I'm not sure what kind of thread to use)
Laxitive for vent gleet:
Castor oil/ olive oil for sour crop:
Corid or Sulmet for Cocci (bloody poop):
Mareks's disease...nothing you can do here, the birds just have to have a vaccination against it (vaccinations come 200 per order, so just hope your chicks got it at the hatchery!):
This BYC page covers a lot more than I did here: