Someone on here,several years ago, when shares were mentioned, said it's just a form of gambling. I disagreed because it's an investment and usually comes with a divi. Yes, shares can go down as well as up, as you mentioned, but with FTSE 100 shares with a solid history if they go down you just wait until they go back up. It's well known that, in the long run, shares outperform deposit accounts. To me gambling is when you place a bet on something, like a horse or a lottery ticket which if it loses so will you. There's no waiting for it "to win." Of course it has to be money that you don't need or are likely not to need...and who knows what's round the corner ?.. and can afford to lose. The "don't need" aspect seems more relevent because an investor may have to wait a good while longer than he/she anticipated before selling at a profit.If someone can't afford to lose an investment sum then they shouldn't be investing.
I just checked Bitcoin. £78,522.20 that's up £3035 today..

50 million people own Bitcoin.About a million own one Bitcoin.
Users on the BitcoinTalk forum traded 5,050 bitcoins for $5.02 via PayPal, making the first price mediated through an exchange a bargain basement price of $0.00099 per bitcoin.
From a November article: "
If you had purchased $20 in Bitcoins from an online forum in 2009 you might have been able to buy over 20,000 Bitcoins. Since a single Bitcoin is worth around $70,000 today, your $20 purchase would have turned into an astounding $1.4 billion!"
I've read that there are people who bought back in 2009/2010 who still hold them. I wonder how much capital gains tax they'd have to pay ?
Re your ex... I've also read that buying the right piece of art is a good investement. As ever, it's very important to be familiar with what you're investing in and I know nothing about cryptocurrencies nor art values an d importantly, recognising fakes.