To budget means that you have put aside money that you can afford from the income you receive. So in this instance you have put into your calculations of income and outgoings that you can afford to open a new branch (another part of the company). If you do not do that then you will be able to afford to buy new machines for the other existing stores. I have budgeted for a new car next year. I have set aside money from my job so I can buy the car.

we usually don't. we say "save for"

"if i don't open the new branch, I can use some of the money I had budgeted for it" - the budgeted is referring to the thing just mentioned, in this case for opening a new branch. You can use "arrangements" in place of budgeted, but not "arrange". Its implying that there is money available to spend. Another way to write it is, I had made arrangements (or...I had budgeted) for opening a new branch, that I choose to spend it to buy new machines for the other stores then rest I can save in case of emergencies.