For nighttime, I've been putting my 8 month old dd in a zip-up bag with arms. Carter's makes them, and I also have one that's some other brand. If it's cold enough, she can wear other clothes underneath it - anything from just a t-shirt to a warm footed sleeper. I figure we can let the nighttime temperature get low enough that she needs a sleeper inside the bag, but not lower. I'm not quite sure yet how cold that will turn out to be. Of course, it's hard to know for sure how warm or cold she is, but I try to judge by how comfortable I am in an equivalent amount of layers, and by how warm or cold her skin feels.
For daytime, I think we're going to have to keep it pretty warm, at least in whatever room she's spending most of her time in. She's reached a stage where she doesn't enjoy getting dressed or undressed, so it's a pain to put her in too many layers. And it's nice for her to be barefoot as much as possible, since she really likes to practice standing and she's starting to work on cruising. Socks are too slippery for standing on hard floors, and they come off too easily, too. We're going to have to get her some kind of soft shoes, but I'd still rather have her just be barefoot. DP thinks she can be barefoot even in a fairly cold room if she has a hat on; I'm not so sure about that myself.