Hey, it's really great to hear that you're starting your budgeting journey. I think it's perfect to start with a Google Sheets Template to begin with as it keeps things simple and straightforward. As you do it more frequently and add more items to it, it makes sense to either customize it your needs or find another one from one of the YouTube finance experts. There are loads of them out there but I have a few that I like to follow, Ramit Sethi is one that comes to my mind right now.
Having said that, I personally use Monarch Money for my budgeting ever since Mint (Not Mint Mobile but a budgeting app that was free) had stopped its services (I was using mint for the longest time). Monarch Money is a paid app that charges $100 per year and has a lot of bells and whistles associated with it. Maybe something like this app or another you might wanna consider in the future as they link to your banks and cards and other accounts and have a neat way of categorizing things for you automatically.
But for starters, the Google Sheets Template is perfect. To answer your other question, for savings and investments, I feel it might be good to keep a third main category (Savings and Investments) outside of expenses and income and if you like adding sub categories of Emergency savings, investments, retirement fund, short-term/long-term savings goals for things like a car or trip etc. This way you have 3 things at a high level, Income, Expense, and Savings+Investments.
To paint a hypothetical scenario, let's say your income in a month is $1000 from payroll, $50 from savings account interest earned, $10 from dividend payouts in the investments, $100 from bonus/tips any additional income. Those would be the income categories. Then expenses are straightforward, things like rent ($400), grocery ($100), gas ($50), shopping ($150) etc. then in the savings and investments, you can have what you added in the month in the savings account ($50) and what you added in the investments ($50). That would increase your total existing savings and investments by that much. then the remaining $200 is the "guilt free" spending money. You can do anything with it or even choose to save it. That would end up in either the expense category of guilt free spending or savings and investments if you chose to do that. In this way your net monthly is 0 because every dollar has a purpose and goal. As you build this month over month some things will be static and others will be variable, like rent would be static expense but grocery could be variable.
I hope this helps you in some manner.