For a newbie (or anyone non-pro really) imo you should:
1. read the uk personal finance wiki
https://ukpersonal.finance/ particularly the personal finance flowchart to make sure investing is the right thing to do
https://ukpersonal.finance/flowchart/ and diy tracker to understand a bit better what you're buying and why
https://ukpersonal.finance/diy-global-tracker/
2. open a stocks and shares isa with a platform of your choice, e.g. hargreaves lansdown.
3. buy a combination of tracker funds suitable for your age and level of acceptable risk, e.g. 80% stocks, 20% bonds.
there are loads so here's a shortlist:
https://www.hl.co.uk/funds/help-choosing-funds/wealth-shortlist
each has a factsheet including: largest holdings, countries/sectors breakdown, fund size, yield, hl comments
don't buy anything you don't understand.
4. leave it alone for as long as possible. don't tinker. don't check it often. don't panic sell if the numbers turn red.
a reasonable way to track the world would be 90% of this
https://www.hl.co.uk/funds/fund-dis...eral-international-index-trust-c-accumulation
and 10% of this
https://www.hl.co.uk/funds/fund-dis...gal-and-general-uk-index-class-c-accumulation
or you could choose to track particular sectors
https://www.hl.co.uk/funds/fund-dis...al-gbl-health-and-pharma-index-c-accumulation
https://www.hl.co.uk/funds/fund-dis...al-global-infrastructure-index-c-accumulation
https://www.hl.co.uk/funds/fund-dis...l-global-real-estate-div-index-c-accumulation
https://www.hl.co.uk/funds/fund-dis...-global-technology-index-class-c-accumulation
bitcoin is gambling, nobody knows what it's worth, if anything.
forex you can't win coz pros have it all automated.
edit: a couple of other interesting funds:
https://www.hl.co.uk/funds/fund-dis...-global-emerging-markets-index-c-accumulation
https://www.hl.co.uk/funds/fund-dis...uture-world-esg-developed-index-accumulation2