For anyone starting out, the amount saved each month matters far more than the return earned on it. Doubling a 5% return to 10% on a small balance moves less money than raising the monthly contribution by fifty euros. The lever most people ignore is the one they fully control.
The mechanism that works is order. Money that is moved to savings the day the salary arrives gets saved; money that is saved with whatever is left at the end of the month usually is not. Automating the transfer removes the monthly decision, and the monthly decision is where the plan dies.
Before investing anything, most guidance converges on a buffer of a few months of expenses held somewhere boring and immediately available. Its job is not to earn: it is to stop you selling investments at the worst possible moment because the boiler broke.
Only after that does investing make sense, because investing means accepting that the value will fall sometimes. Money you might need in six months should not be exposed to a market that can be down 20% for a year.
A useful frame for a student budget: three buckets. One for spending, one for the buffer, one for the long horizon. The third one is the only one that should ever be invested, and it is the one that benefits from being left alone.
Educational material. Not investment advice.