It all depends on your size, age, weight and strength I'm afraid.
Many longbow orientated clubs (although there are not huge numbers of these) will have equipment you can borrow until you get a real feel for what you need.
We (
www.cloutabout.com - Clifton Hampden Longbow Society) have a couple of 'club bows' at 40 and 45 lbs which we feel are ideal average beginner weights, 50 lbs may be a little on the heavy side for a beginner (it is not just about raw strength) but it depends on the individual.
Where do you live ? If it is anywhere near us feel free to visit one weekend.
TimS