Having a fix percentage is going to be a nightmare to maintain but it's perfectly fine to have some numbers to use for measurement. One important factor to consider is that when you don't have much money to investment you don't have much money to lose so at that time it doesn't matter too much how your investments are divided. It's also important to know why you're dividing your assets and then how.
That being said, in the beginning you can consider going for higher returns with less division between different asset classes until you reach a peak where a big loss within that asset class would be deemed devastation by you. That's if you're trying to reach a maximum gain. Some might be uncomfortable with high risk at all but one can argue that chasing pennies is a risk in itself but that's for one self to decide.
At your age (and for anyone with a low net worth really) the most important factors are reducing living expenses, without cutting out your entire quality of life, saving up enough money to actually investing in something meaningful and then learning how much of your investments you want to have passive (lower returns, lower risk) and how many you want to have active (higher returns, more work or more risk).
I'd take a look at the book "Set for life" by Scott Trench (Audible available). He talks about these important steps in the order they make sense for your journey. He does talk about diving your investments and how it should be considered. His insights should provide meaningful to you. He's financially free and to do that he's combined traditional methods from guys such as Dave Ramsey and then intervened it by channeling his money into investments such as real estate and index funds.