What's a simple beginner budget I can start today without any apps?

You can build a working budget in 15 minutes with pen and paper or a basic spreadsheet. Write down your monthly take-home pay, then list fixed bills and subtract them. Take whatever is left and split it three ways using the 50/30/20 idea as a starting point: needs, wants, and savings-plus-debt. Set up one automatic transfer to savings so the savings portion happens without effort, then use whatever remains for spending. Do not aim for perfection or granular categories on day one; the goal is simply to know your numbers and pay yourself first. Refine it after a month once you see where money actually goes. Starting simple and sticking with it beats an elaborate system you abandon in two weeks.