If you're in the UK, open a stocks and shares ISA.

Do it today. Here's why:

It allows you to invest £20k per year TAX FREE. No taxes on gains, forever.

It's one of the best long term vehicles for tax-efficient investing in the UK. I can't stress how great it is.

Whatever disposable monies you can afford to kiss goodbye to each month, chuck em in. Doesn't have to be a lot. £100, £20, £10 a month, it all adds up long term.

Investing is not just for rich ppl or for ppl with money. EVERYONE should invest, doesn't matter how much. The goal is to beat inflation and protect/grow your money. Doesn't matter if its just £10 a month. It adds up. Your fiat currency is being debased year after year. You must protect yourself.

Personally, I buy S&P500 and Nasdaq100 index funds with a 30+ year time horizon. It's up to each individual person what they buy. To each their own.

Short term, you shouldn't care if price up/down. Be a robot with no brain. Robot invest every month. Robot know number go up long term. Robot know mechanical investing will make money grow.

S&P500 average yearly return since inception: +10%
Nasdaq100 average yearly return since inception: +14%

Some large/liquid ETF options:

S&P500 unhedged:

$VUAG (dividends automatically reinvested)
$VUSA (dividends distributed to u in cash)

S&P500 hedged:

$IGUS (dividends automatically reinvested)
$GSPX (dividends paid to u in cash)

Nasdaq100 unhedged:

$CNX1 (dividends reinvested)
$EQ (dividends distributed to you in cash)

Nasdaq100 hedged:

$EQGB (dividends reinvested)

FX hedged ETF's take away fx risk (for the most part). Example: if GBP strengthens against USD, it will negatively impact ur unhedged holdings beyond the instrument's performance. Nasdaq can be +10% for the year, but if GBPUSD also rose +5%, your return would be ~ +5% (napkin math).

Vice versa, if GBP weakens against USD, it will positively impact your unhedged holdings beyond the instrument's performance. Nasdaq can be +10% for the year, but if GBPUSD dropped -5%, your return would be ~+15% (napkin math).

Upside: fx risk is taken away and therefore your investment is a pure bet on the instrument's performance
Downside: higher fees

I personally hold a mixture of both hedged and unhedged. Good to note that long term over decades, fx fluctuations tend to iron out / mean revert anyway but can be painful year to year (like in 2025: GBPUSD rose a lot).

I'd include crypto exchange traded products in here however the wonderful UK government are banning them from stocks and shares ISA from April.

Worth noting too, ppl are too afraid of timing the market. 'What if price goes down?' - if you're just chucking spare change in there every month, price going down is good, you get cheaper price. Investing a lump sum is another discussion entirely whereby timing does matter, that's a discussion for another day. If you're dollar cost averaging every month with a long term time horizon: the early you start the better.

Long term example: £100 invested every month for 30 years with a +10% yearly return: ~£230k+ (with only £36k invested). Rough math, not including fees etc. All tax free when you want to sell within a S&S ISA. This is assuming the UK government doesn't abolish or fundamentally change the S&S ISA btw.

Disclosure: this is not financial advice. Investing can be volatile/risky, focus long term, always.