I have been a councillor. It is incredibly hard for parties to find enough people willing to do the donkey work of campaigning, leafleting etc and party membership in general has been declining for years. Look at the people out campaigning for the Tories and they are overwhelmingly pale, male and stale. Younger people tend less towards party membership and more towards campaigning on single issues.
It's a bit of an issue that you're not even sure which party you'd want to be part of. Sort that out, join the party, get out and do the tedious foot slog, offer to stand. You might have to stand in a "less winnable" ward first but most parties are actively looking to recruit candidates.
Being a councillor is effectively a fulltime job but you're paid an allowance of maybe a few hundred pounds a month (obviously taxable). You will have to sit through lots of meetings, become informed on the minutiae of day to day management of a local authority (weekly bin collections? reduce lunch clubs for pensioners?) and accept joint responsibility if your party decides something you dont agree with.
You will spend a huge amount of time doing casework on behalf of your constituents (my bin wasn't collected, my elderly mum can't get a carer, my family are overcrowded, my next door neighbour's child is on the trampoline every day at 3pm, we want residents' parking, we don't want residents' parking, nothing ever happens in our parks, why is something happening in our park?) and you have to work on their behalf, even when you don't agree with them.
Your public profile is everywhere. People come after you on social media. People are rude and aggressive (and so proud of themselves). Post about something you care about and the hate that comes out of the woodwork is extraordinary.
Your bio will be published but you can emphasise some bits over others. Whether or not you currently work will be far, far less important than which party you are standing for; most voting is tribal, habitual or protesting about the incumbents.