I have a garage with just the shell of a fuse box put up, but I now need some electricity, not a lot, in there. Should I finish the fuse box or just run an extension cord from the house with a 3 way plug-in?
If you put circuits in the box, you can always just put in what you need. You don't have to fill it up. If one 10 amp circuit can service 5 regular outlets (which it does) and that's all you need, just put that in. You wouldn't even need a breaker bar that shuts the whole thing down.
But it sounds like you might want to read up on this. Electricity isn't a guessing game.