the playstyle and build of each class varies - you build up to a concept with the features that you choose, which in turn adapt the method in which you can best play your character. For spellcasters, this is usually in the building of your spell list; for rog...
You can't use a weapon as a spellcasting focus, but you don't need it for everything. On Multiclassing: I now turn you over to the erudite PeteNutButter: http://www.giantitp.com/forums/showthread.php?502248-Ultimate-Optimizer-s-Multiclassing-Guide Yes, I cheated a bit in t...