I'm a relatively inexperienced photographer with aspirations of someday producing pro-quality photos. While it might be nice to go out and buy a lot of fancy equipment, that really isn't an option; I can only acquire things over time (like, years) as my budget allows. Also, I'm something of a minimalist, and I'd rather have one piece of equipment that can do the job of two, even if it won't do it quite as well.
Right now I have a Pentax K-7 with 18-55 weather resistant lens. For editing I have Corel Aftershot, and a Spyder 3 screen calibrator which unfortunately doesn't give very good results with my laptop screen. My main area of photographic interest is anything outside: landscapes, wildlife, sailboats, trains. I often walk in remote, rugged areas and have to carry my gear in a pack.
My question is, what is the minimum equipment that I NEED right now, to take at least pretty good photos and give me a chance to improve my skill? What should I get as soon as it's convenient? And what can wait a while?