You should take between 5 and 10 pills a day. Some people take higher amounts. I am just going by what MS and wilson6 recommend here, which is 1.5gr - 2gr of total EPA/DHA per day.
I usually take 2 tbsp of UDOs and 5-10 salmon oil pills daily.
flax requires conversion which decreases in efficency as we age. Therefore I jsut take the fish oil, although the essential fats in flax are also good, the studies done on the positive effects of efa's have been done using epa/dha.
Bullit check out www.walgreens.com. They have a cheap fish oil that I have been using for a while now. You should aim for around 6g of combined EPA/DHA per day. That equals out to about 20 caps daily. Even lower doses (around 3g a day) will have some good effects for you.