By your description, I would say that a used Suzuki DRZ-400S, Honda XR-650L, Kawasaki KLR-650, or if you are really cash strapped an old Yamaha XT-350 would all be excellent starter bikes for you, as long as you don't do much freeway commuting (they all have very short gearing so they would rev an buzz too much for long freeway stints)
If you want a cruiser and only a cruiser, try the Honda Shadow 750 or 1100, or the Yamaha V-Star 650 or 1100, Suzuki Intruder 800, Harley Sportster 883 or any other 600 - 1100cc "cruiser" none of them are waht you would call "fast" and they tend to be quite reliable. If you really like this class, stay tuned, because we'll be doing a "Middleweight Cruiser" comparo in about 30 days.
Hope this helps -Sean