This is a wrong attitude and I really don’t understand why many brokers put this kind of statements in disclaimer. You should gamble what you can afford to lose. You should invest money that you don’t need next 10 years (although there are some nuances with the use of margin loans).
Going back to your original question: you can start investing into a all world stocks ETF on mustachian terms from 25 EUR:
You can also buy a partial share of VT at Interactive Brokers, but each currency exchange costs 2 USD and each transaction costs 0.35 USD.
Also consider investing 3a money.