Beginner's Budgeting Attempt

Now that I'm finally working again, I need to start working on the life improvements that I haven't been able to work on because they required money. The problem is that I have a huge list but I'm only working part-time. So in order to do the things I want to do, I need to watch my money like a hawk. I was incredibly fortunate in the past. I was making plenty of money for my lifestyle and didn't have to be very careful. Now, I have to be extremely careful. I've almost created a plan, I'm stuck at one part though. I'm a bit nervous about how implementing it into my life is going to go once I complete it.

The first part of my plan is to keep track of a monthly budget and actual spending. I found an Excel template that I really liked, except that I found it difficult to personalize. So, I just made one inspired by the template I liked. I've taken Excel classes so I know it well enough that making a template is pretty easy. However, that is the only easy part. Figuring out the numbers was a huge pain and I'm pretty sure that they are going to have to change as the months go on. I plan on printing it at the end of each month so that I have record of it and can track how my spending changes over time.

I am also religiously using my transaction register that came with my check book. It's a great way to keep track of how daily spending affects my bank account. Every single debit and credit gets logged in that thing.

The part I'm having trouble with is how to keep track of my budget when I am actually shopping. I've broken down my budget, giving myself allowances for things like clothes, toiletries, and groceries. But I haven't figured out how to keep that budget on me as well as keep track of how much I've already spent on each thing. I hope that made sense. How do other people watch their budget when they aren't at their computer? Do they just print it off and keep it with them? Or do they have a separate sheet that tracks spending and categorizes it?

Once I come up with a solution, I'll be on my way to hopefully having a budgeting system that works for me. I'm a bit stuck at the moment though.