Maggie gets fish oil daily (on days where she doesn't get a meal of cooked sockeye salmon). We also had her on Cosequin DS + MSM (gluc/chond + MSM) until recently. Since she's on a non-kibble diet, we recently added a vitamin supplement powder call Newf Warrior that includes a high does of Gluc/Chon + MSM. That would be overkill for you I think.
Regular, human grade from the drug store is fine - you can search here for the dosages. There are tons of threads on supplements and others give a lot more than we do!