I realize this is a broad question, and it will depend in part on the type of photography you're specializing in. With that said, let's say you decide you want to make a full-time living as a pro photographer. What would be some of the first items you would purchase - your Top 10 pieces of essential gear that could be used in different shooting situations, including stock photography?
1) DSLR, two minimum
2) The best lenses on the market, not cheap knock off lenses or kit lenses.
3) Camera mounted flash ETTL - with diffuser
4) Monopod
5) Spare camera batteries, flash batteries, second charger 12V and extra memory cards
6) Camera bag(s), lens protectors, rain gear, comfy shoes, wide brimmed floppy hat to keep the Sun off your head and viewfinder

7) Editing software - Elements is actually just fine for photo work, but if you are spending, Lightroom.

Fast computer with loads of memory and a high quality color balanced monitor. It makes no sense to shoot pictures and try to edit them on something that doesn't show what you really have.
9) Good solid tripod and remote shutter release
10) Retirement pension that pays all living wages so you don't need the pro-photo income, or optionally independently wealthy.
Things you won't need: (to start with)
Big Ass color photo printer (or any printer!)
fancy "studio"
Photoshop
Ball head for the monopod, or some carbon fiber device. A stick with threads on the top will work!
reflectors,
soft boxes,
umbrellas,
Lighting systems,
wireless remote strobes
white balance cards
all kinds of other devices and toys that are not essential to taking good photos,
most of the filters (except carry a CPL just in case you need one!) and I use UV to protect my lenses but that's a whole debate in itself
Details depend on what you are shooting and what direction you want to go.
Start with the essentials and fill in the rest as your path defines itself.