Brought my late stepfathers rifle home a couple of weeks ago. It's just a very ordinary Sears semi-auto from about 1972. I want to put an inexpensive scope on it for fun & plinking out to maybe 50 yds, probably shorter. I know less than than nothing about optics. What power would work for me? Fixed, adjustable? I figure there won't be much quality difference in the bottom-feeders I'll be considering, but any I should look for or avoid?