Omega 3 Supplement Benifit if eat weekly some canned fish /smoked salmon

Is Omega 3 sup0plement necessarily a benifit and is Omega 3 and 6 combined necessary or just 3 for OA and muscular/vit D deficiency (take D&K vitamins currently)G-P said i have a huge Vitamin D deficiency.I live North Scotland so like Finland serious D deficiency not to same level as Finland obviously. P lease any recommendations and a good quality supplement and how much dfoes a decent Omega 3 ?and 6 combined cost. Any research information on Omega 3 effectiveness? please. I have thoroughly trawle4d online but all advertising features.