I have a recipe for the budget problem - I get only 1 or 2 new ornaments every year, and sometimes they're even handmade i.e. recycled old ornaments (for example this year I figured I have 2 old glass balls and will apply cotton balls to them, making snowball ornaments). That way I can have a natural tree every year. I also don't have two dozen sets of lights (I have just two sets), and for a sparse tree you really don't need a lot of ornaments altogether. I also find some pinecones and other free stuff (my old ceramic figurines, dried flowers etc.) and transform them into ornaments. I also don't have a color scheme and the lights are multicolored, so combining that with a natural tree makes it impossible to decorate exactly the same way two times (there are no two identical natural trees).
And regarding you decorating the tree early on, well, I heard of people who bought trees with a root (common thing here) and planted them in a pot before decorating. After holidays they just took the whole thing on the balcony or in their garden, watered and nurtured during the year and had the same tree not just next year, but even for 5 years in a row! Of course there's no gurarantee that every tree will live like that, but they say it's worth a shot.