I don't have a percentage for trading because when trading the capital used is savings that I deliberately took out because I thought this could be doubled if I succeeded in trading.
And now if I want to trade, I also do the same thing, just take savings but only when I see a good opportunity, such as when the market drops quite deep, I will enter by buying 1-2 altcoins with good marketcap.

If you want to use it from your monthly income or regular income, maybe no more than 5% or based on funds that you can actually separate and if lost it will not affect your finances during that time.