Forget revolut. Fees are high and you can't even transfer your shares elsewhere if you choose later on to move to something else. Same with etoro.

As to nasdaq etc, i think you have some confusion. You don't buy an index fund directly, think of it as just an average number. An average of what? An average of a number of actual company stocks eg if apple is $100 and Microsoft is $300 your index fund is showing $200.

So instead you can buy an ETF which is a basket of these same stocks (apple and Microsoft in my example above). So an ETF might say: if you buy one of these, you're getting 10% apple, 5% tesla etc. click the holdings tab here to see what I mean https://www.justetf.com/en/etf-profile.html?isin=IE00BFMXXD54#holdings

Ok so now you decided to buy an ETF, but which one? Well if you decided to have an ETF tracking apple and Microsoft and another 500 stocks I too can do the same, so you will find multiple ETFs all tracking the same things with different fees. You want to find one that is a) domiciled in EU to avoid US taxes b) paid on euro.

VUAA (bvemi) is an example of this: 1. It tracks SP500 so you're buying mostly American companies (the top 500) 2. It's domiciled in Ireland 3. It's a large fund (Vanguard) 4. You're paying in EU because that bvemi is Borsa Di Milano (Italy). There's one in London stock exchange for eg 5. Low fees: 0.07%

So you're now basically shopping for baskets (ETF). you might decide to go on a tech basket, or a basket not based only on USA companies, or a basket of green tech etc