As for the UK, property could give you decent return in relatively short time. Aim for cheaper houses (< GBP 100k, affordable for first time buyers), preferably repossessed by bank, located within less than 1 hour drive from the town centre of any major city. Don't do any major work on it, just refresh the look, give it a proper cleaning and re-paint.

If you're lucky, you can pocket out 30-50% profit in few months. If you struggle to sell, you can always try to rent it out.

As for Bitcoin. Definitely too risky to invest large % of your wealth in it. But as someone said on this forum: you have to be clinically retarded not to own some, just in case.