I inherited a cokin a-system (a system = amateur, smaller, probably not made now, P system = professional, larger) set from my dad. It's a smaller system but fits the 49mm thread on my 50mm prime lens. Haven't got any grad filters for it yet.
London Camera Exchange near my work have a big box of secondhand filters, so might pick some up for pennies.
I have used the grad filter in ACR a number of times, and it's ok, though I can't seem to get it to do black grad filter very well, just colours.