On the OP question I personally have used binance. They have their issues with the FCA though, so read up yourself before choosing to use them or any other exchange (FCA site has some useful information about which companies are registered or operating under temporary registrations -
Registered Cryptoasset Firms (fca.org.uk))
I am in now way any sort of expert, but a couple of things I have learnt over past few months buying various crypto -
Treat as gambling, ONLY spend what you are happy to lose (spend your beer money on it, not your rent money)
It is a rollercoaster, the prices can go up and down wildly, so stay away if this will bother you or you are risk averse
Don't ignore the tax implications, and depending on what you are doing, it could impact capital gains and/or income tax, and some areas I still have no clue what tax implications could be
Ignore all the people shouting to HODL. Buy and sell as and when it suits you and your needs
Move the coins off the exchange after purchase to a personal wallet
Don't buy into the newest meme coin without reading up on it first (read about SQUID token to see what can happen if you don't do some diligence and read the whitepaper before buying)