When developing software, I am very finicky about my environment. My productivity can drop significantly for small issues.
I like bright white lights, especially fluorescent. Perhaps, the human brain is conditioned to awaken and become more alert at the presence of light, and white light may be more natural than yellow light. Turning on more lights proportionally increases my alertness as well.
My leather chair, which costs me between $100 and $200, is comfortable and ergonomic. Since I spent so much time on it, I was willing to put in some cash. The time and productivity loss from having back and neck problems is real. I also wanted to make sure that the chair doesn't break easily.
I also need a file cabinet. Everything in the file cabinet is organized and close at hand. I try to minimize my need for the file cabinet by scanning important documents and storing them inside the computer. I like to leave lots of space in my room to do reading or design work on paper. I also have a place to rest in the same room, when I grow tired or need to think heavily about a problem.
I keep everything that I need or use frequently nearby to minimize the travel time and reduce the distraction level. My phone is close by, but out of the way. My supply of water is two steps away. I have four bookshelves. My bookshelf, consisting of my most frequently accessed books, is a few steps away as well. My other bookshelves do require a short walk. These bookshelves contain current, useful books. Periodically, I remove obsolete books and sell them to a used books store; then, I walk through Barnes and Nobles or browse Amazon to look at what's new. I often pour through a book on technology that I have never heard of to expand my mind.