Recently a question on Stackoverflow reminded me of that rookie coder. Being fresh out of college gives you an amazing combination of overconfidence and cluelessness. Without any basis, it's easy to take the office attitude and run with it. You shouldn't have to buy your tools, your company should.
Why? Because they are tools. It's not even a cost thing. A professional should be responsible for knowing which tools they need to be most productive. Tour an airline maintenance facility and check out the workshop. A large area, maybe 1000 sq. ft., with nothing but large toolboxes; each with a name and a lock. The mechanics have to buy all their own tools, think wrench sets and so forth - not large things like engine dollies.
At first it seems a bit silly and redundant but when you start to think about it, it's easy to see that not everyone is going to want to spend the extra money on the high-end tools, or they might want extras of the same set for whatever reason. Also, consider the hassles with sharing, e.g. "Where are the 1/2 inch box-end wrenches?" By not making the tools shared, the 'Tragedy of the commons' is avoided.
Another example is chefs and their knives. You don't touch another chef's knives. The restaurant provides the big things like ovens and stoves, the chefs bring their own knives.
Back in the world of computers, I've brought in extra memory before. I told my manager so he'd know that some of my personal property was in the PC in case it needed to be worked on by the internal techs. I also put a note on the box itself. I would have had a bigger issue if they discouraged bringing your own hardware. Most shops like to provide the box itself because it minimizes their support issues but they shouldn't have any problems with you bringing accessories like monitors, keyboards, mice, etc.
To summarize, change how you think about tools and strive to use whatever makes you better at your job, even if you have to pay for them out of your own pocket. It's the 'Professional" thing to do.