I Dollar cost average (DCA) in index funds and ETF's that reflect markets that might keep growing. I'd be weary of individual stocks or even crypto... unless you go long on your buys.
If you don't know what DCA is, it's basically a technique that entails investing a fixed amount of money in the same fund or stocks every month over a long period of time. That fixed amount is usually a percentage dictated by you, when you analyze your finances. (How much can you invest out of your paycheck every month, the more you put, the more money you'll have working for you.)
I wouldn't park money on a savings account, you're loosing money to inflation, your money is literally loosing it's value every year (2%/3% annually on average, more so in 2021) so you need to make sure you're hedging for inflation at the very least.
If you don't know what hedging is, say inflation is 3% that year, and you have all your investments on the S&P500, which makes on average 8% a year. You actually made 5%. So you didn't loose money to inflation, you actually made some back since you put your money to work while you slept. That's hedging in a nutshell as I see it. There's other ways, gold, silver, real estate, etc. They're called assets (vs liabilities).
That said, it's wise to have some money saved, it's called a emergency fund (usually enough money to survive 6 months without being employed, case anything goes wrong and you need access to cash, fast) to have more money than that pile up on a savings account, is widely regarded as a bad financial decision, since that money isn't being put to work for you, your bank does it for you without you even knowing, and you only see 0.01% back in interest.
As for which Index Funds you think are the best, I always revert to index funds that reflect the whole US stock market, and other index funds that reflect the international market, and the S&P500. You're basically investing in thousands of companies at once, it's a big basket, so even if one company does horribly that year, you have all the others affecting the average, these things historically keep going up, decade after decade.
If the market is down, you buy. If the market is up, you buy. You don't need that money tomorrow anyway, this is mostly for retirement so forget about daily, or even monthly market fluctuations.
In the US there's retirement accounts like the RothIRA where your investments grow tax free, and others like the 401k where you invest your money before it's taxed (usually through your employer), study what options you have in EU / your country for retirement accounts, and look at the expense ratio of the index funds that they offer. The sooner your start DCA'ing, the sooner you can retire.
As for crypto... I allocate 5% of my total portfolio to cryptocurrencies. It's a riskier investment, but having some exposure to it, so far has been my best decision in terms of investments, even with such a low percentage.
As for which crypto to buy, I simply DCA on BTC, ETH, ADA and leave most shitcoins alone.
As thiago said, dedicate some time to read about this shit, you'll be thankful you did when you get old.