the thing you might want most is a filter - whilst plaits has one built in, it's a good idea to get used to using one and willl give you more flexibility - also I'd get the utilities I mentioned (or similar) earlier rather than later - they'll help you get your head round patching more, especially combined with working your way through the maths illustrated manual a few times
"some of the best base-level info to remember can be found in Jim's sigfile" @Lugia
Utility modules are the dull polish that makes the shiny modules actually shine!!!
sound sources < sound modifiers < modulation sources < utilities