Dosage ranges are really wide and there is little chance of overdosage on either.
Glucosamine 15-30 mg/kg
Dogs >50# 3 capsules per day split 2 am or pm 1 at the other time (Cosequin DS)
Essential Fatty Acids (fish oil - EPA,DHA) again a really wide range 22-40 mg/kg/day. Again it's hard to overdose - you will get GI signs with higher doses.
One note, if you use human product, DON'T use one that has Flax or Flax seed oil as the source as dogs and cats are not able to metabolize that form - you'd be wasting your money. Stick with the marine source - real fish oil.