if i was to do a DNA test which one would yous recommend ??
The best way to approach it is first to decide what it is you want to find out.
YDNA - can only be taken by men and only gives the direct male line ie father, grandfather, great grandfather etc. Can be useful in helping with surname studies
mtDNA - can be taken by men and women. This gives the direct female line ie mother, grandmother etc
Autosomal - can be taken by everyone. This looks at all your DNA (albeit based on a very small sample) and is what is used to determine your ethnic\regional origins (although this is more subjective than objective as the science is in its infancy). This tests is also what is used ti find potential relatives hence its alternative name of family finder.
With all tests what you need to remember is that only a very small percentage of people have taken the tests and then mainly in America so you may have to wait a long time to see results that are meaningful or there again you may hit lucky and get productive results straight away - its a gamble