If supplementing omega-3s, I generally recommend cod liver oil if it is tolerated by the client. Cod liver oil is less processed than other fish oil products and is naturally higher in vitamins A and D.
Nordic Naturals is a good brand that is easily available and affordable. Fermented cod liver oil is also a good choice for those clients who will actually take it.

Fermented cod liver oil is more expensive.
You can take cod liver oil in capsules, but just note that you will need many capsules for a therapeutic dose.