I used to troll with downriggers quite a bit in the Pacific NW. I had Scotty electrics with 4'adjustable booms. I had them for 12 years and never had a problem, besides replacing the cable due to saltwater corrosion. However Scotty electrics run about $400 apiece. Electrics were good for salmon fishing becuase when you hooked a fish you needed to get the downriggers balls out of the water because if they wrapped the mono on the cable it was goodbye fish. We also trolled at depths typically 100' to 150' so manually cranking up one or two downriggers when a fish was on added some unneeded excitement and stress.
However I would imagine fishing the lakes around here you won't be fishing very deep so you could get by with manual riggers. I have had Cannon manuals before I got my Scotty's and they worked fine. Scotty also makes manual riggers, I'm sure they work fine also.
I would think you could use 6-8 LB balls to troll with, the faster you troll, the heavier weight you need to keep your lure at the exact depth you are targeting.