I've thought about this a lot.
For flat surfaces and edges a good jack will do almost everything.
The main advantage of also having another (smoother etc) is it can be kept set-aside and sharp and ready for smoothing, but the jack can do it all if necessary.
Then there are rebates and slots. A plough planed slot can also become a rebate or a raised and fielded panel if the waste is removed with the jack.
But if you don't need slots a rebate plane would be good.
So that's it then; ignoring mouldings, for almost everything else all you really need is a jack and a plough plane. A block is also handy.
The marginal advantage of having more planes is small (and diminishes) and for a beginner is probably negative.
