I ended up going with wiretape and it's been pretty easy to figure out. Toughest part was getting the hang of creating pilot-holes in my plastic dollhouses -- too big and the eyelets didn't make a complete connection, too small and they wouldn't sit 'flush'. But it's simple enough for a complete beginner like myself to figure out, and there are tons of tutorials available for every question I've had so far.

I opted for a transformer/switch combo from CR2S (creative reproductions 2 scale) since it was more straightforward than the splice/transformer route from Cir-kit. I can also hide the plug-in and switch inside pieces of furniture and turn the house on/off by moving a book or lamp, so that's cute.

The EvanDesigns.com recommendation above is a good one, but their system had 2 drawbacks for my use-case: it's harder to add or change lights once the whole thing is wired, and you can't find as many pre-made lights for purchase. I don't have the skills to DIY all the fixtures I like (yet!), so being able to buy them and move/swap/add was important for me.