I give canned salmon rather then oil; goes much farther...dogs enjoy it better.
Joint supplements - my big guy is on Natural Stride powder; my girl is on Phycox Max - both have been on joint supplements since they were 6mnths old; no visible arthritis in my 7yr old boy.
Vit E - 400 IU's every few days
They each get a teaspoon of kelp/alfalfa powder mix every 2-3 days.
That said, both of my dogs are over 18mnths of age; both are on a raw diet.
I would *not* be giving certain supplements if the dog is younger then 18mnths of age, exception is a joint supplement - can be started at any young age.