Disclaimer: I work in accountancy (Commercial Finance) but my advice should be taken with a pinch of salt.
Diversify your investments. Have savings across multiple bank accounts so that the unlikely event where one bank fails doesn’t wipe out your financial wealth., and overall don’t put your eggs in one basket.
Currently, the best ROI/passive income you’ll get is from corporate bonds. A cursory glance at the Hargreaves Lansdown website shows me quite a few corporate bonds and gilts that have a voucher rate (% return each year) of over 8 percent. Do bear in mind that a bond is a loan instrument where the ROI is based on both the maturity date (the date you get paid back plus interest) and the overall risk of the debt.
Another good option is to invest in high dividend yield shares or ETFs. These can offer superior returns on investment to the interest you’d get from a savings account.
Avoid day trading or swing trading unless you 100% absolutely know what the fuck you’re doing. Unlike what many YouTube ‘gurus’ claim, making a living off the stock market requires a high amount of starting capital to see any kind of tangible ROI, plus sophisticated stock trading software and knowledge on how to exploit trends.
Same goes for penny stocks (i.e. the FTSE AIM All Share market.) You can make some rookie gains from it. Many of the companies listed on this index are oil/gas/mineral exploratory firms that are likely not going to see any kind of profit unless they strike it big, find a new oil well, lithium mine, etc and get the necessary contracts and investment to extract those resources. They’re penny stocks for a reason.
Side hustles. For example, I have two friends that are karaoke DJs and they get gigs where bars pay them to host nights. Bookkeeping is another one, but you really are going to have a lot of competition in that respect, and you will probably need the right qualifications to do it.
Screw crypto. At best cryptocurrencies are speculative assets that are scarce and expensive because the very nature of how their blockchains were designed make it take exponentially more effort to mine a new coin. At worst, they’re used to launder criminal proceeds (Monero is a good example of one where the blockchain is encrypted.) NFTs are even worse.