Marketing is a big area so it depends on your interests. The agency world is desperate for staff but it can be long hours and poor work/life balance.
^ agree with the above (incl the agency warning). I have over 20 years experience in a specialised field of FMCG marketing - and while I have a broad idea, I could not do a general brand marketing job as all my experience is in my speciality
You don’t need a Masters
Some kind of basic marketing course would not hurt as an overview & to show commitment (eg online short course). CIM is a bit old fashioned but equally would give you the basics
Thinking of FMCG brand management salaries (in London)
Entry level jobs are not v well paid (no idea as I’m not at that level but maybe 30s?).
Colleagues with around 8 years good experience are doing well to earn about 50-60k as brand managers/senior brand managers.
80-120k would be a v decent salary for someone senior (director/head of) - 15 plus years experience, maybe up to 200k if heading up a large team but that’s unusual
Nowadays, the most desired employers are tech (google etc) and pay well but tough hours
I think you should try to home in on the area that is the right fit for you - look at the Marketing Society website & CIM to see what appeals
What kind of organisation do you want to work for (a manufacturer, a media company, in education, public sector etc ) - there are marketing roles in all of these
Can you try to do informational interviews- eg can friends introduce you to the marketing teams in the organisation they work for?