What age are you as that may influence some of your decisions. When you say you're a carer do you mean a "family" carer on Carers Allowance or a paid carer (eg in a care home)?
If you're earning you can pay the equivalent of your yearly salary (up to £60,000) into a SIPP and get tax relief on it.
It's worth knowing that even if you're not earning (eg you're on benefits - no salary, not self employed) you can put £2,880 into a pension every year and the government will top it up to £3600.
If you earn less than £60,000 (or in your case maybe are an unpaid carer on benefits), but want to pay in the full £60,000, you can make a non-relievable contribution to make up the difference - eg if you're an unpaid carer you make a contribution of £2880 and get tax relief of £720 giving you a contribution of £3600. You can than make a further non-relievable contribution of £56,400. Brokers/pension funds don't have to accept non-relievable contributions and of the well-known brokers Hargreaves Landsdown is the only one I know of that allows it. You have to phone them up to do it.
If you had a pension scheme set up but didn't max out your contributions in previous years, you can use the pension carry forward rule to take advantage of any unused allowances in the previous three tax years (the annual allowance used to be £40,000 p.a.).
A couple of sites about SIPPS (self-invested personal pensions):
https://www.which.co.uk/money/pensions-and-retirement/personal-pensions/what-is-a-sipp-aBlOf9l200cM
https://www.moneyhelper.org.uk/en/pensions-and-retirement/pensions-basics/self-invested-personal-pensions?source=mas
In terms of investments, you should have a think about your age (& when are you hoping to access your pension) and how risk-adverse you are. If you search on the Moneyvator website there are articles that help you understand your risk profile. (eg this one: https://monevator.com/what-you-need-to-know-about-risk-tolerance/ )
As nannynick pointed out be careful to understand how fees can affect your investment.
Also, don't ignore ISAs as part of your planning, especially if you're young enough that you won't be able to access your pension for some years.