ISAs - if at all possible use it or you will lose it, put in as much of your allowance as you can afford , whilst interest rates are low at the moment they won’t always be this low, if you don’t use your allowance you don’t get another chance to put it in in later years and any future benefit is tax free ( at the moment )
This is important - some sites say that there is no need to use your ISA allowance as you can have up to £1k interest tax free. But that is only per year, whilst the ISA is tax free for life (under the current rules). If you save over your lifetime, you will exceed the £1k interest free limit. That’s when you will be glad you filled your ISA.
There is a limit as to how much you can invest in an ISA each year tax-free (£20,000). This is reset at the start of the financial year. For the new Lifetime, ISA’s the government will add an extra 25% to your contributions up to a maximum of £1000 per year. This also resets in the new tax year.
The Lifetime ISA has an age restriction. Personally, I signed up for 1 as I was approaching the maximum age so thought I better get 1 and pay some into it. I can always pay more later now that I have it.