Freetrade offer commission-free trading via there app. They have a range of ETFs/bonds/US stocks as well as UK and European shares.
They also offer Fractional shares for US-based stock so you can invest in a company at a level your happy with.
They currently are offering Free shares up to the value of £200 for new accounts via the image/link below
*You are required to fund the account before you get your free share but £1 is enough to unlock it!*
If your looking to expand your investment portfolio and are leaning towards cryptocurrencies Coinbase would be your best bet.
There currently offering £7.21 worth of bitcoin when you buy £72.1 and have programs to earn free crypto by doing simple quizes!
Binance have a great app that I find really user friendly, They also have a huge selection of staking coins and interest payments on your crypto!