If you have an old or extra artificial tree – the kind where the branches hook into the trunk but are completely removed before packing tree away – those loose branches work wonders to fill in “gaps” in your tree. Do not worry about matching the greenery styles – it actually looks nice to have a variety of greens on the tree and this is what I would say is the “base” layer – it’s going to be a backdrop anyway – not the focal point.
Larger picks and sprays – both those that are all greenery, greenery with pinecones, or even those with sparkly elements – poinsettias, what have you – if it fits your tree décor style and it’s a good size then it I a candidate for filling in those gaps in the branches.
Remember to stand back and let your eyes slightly unfocus as you look at the tree as a whole – from multiple angles – you will probably spot other “holes” to fill in.
Large and oversize Christmas ornament bulbs, strategically hung, also serve to disguise bigger gaps. I start with these after the lights go on and then move on to all the other ornaments from there.
I totally vote for adding lights in vertical sections by the way! It is so much easier to put up and take down, especially on my 12 ft tree!!!