If you buy yourself anything this week, make it a little notebook. Why? Because this is a way to record ideas, write down observations, and recall details. When was the last time you had a great idea while in the shower or driving? But by the time you get back to your writing, sometimes days later, you've forgotten that idea.
Having a little notebook handy will solve that problem. Purchase a LITTLE notebook. Something that can fit in your pocket or purse. Throw a pen into your pocket or purse also. Any time you have an idea, write it down. When you see something exceptional, write down the scenario, paying attention to the details that make it exceptional. When you think of a name for your character, write it down. When you read something inspirational, write it down.
Then when you get back to your writing, you will have those little details recorded. You can simply flip through the pages and find that name, or re-read that scenario. You won't have to rely on your memory. This will not only be a huge time-saver for you, it will supply you with many story ideas for weeks and months to come.
If you don't want to carry a notebook, purchase the "Notes on the Run" system from Planner Pads. This set of index cards, along with its leather jotter make this a handy tool for writing yourself notes while out and about. http://plannerpads.com/holders.asp