Ok, you need to treat this like a job in itself.
Firstly you need a job. Any job. That’s your immediate term goal.
Then think of the long term. What do you want long term? Is it realistic? Where do you want to be? How would you get there?
On the back of that, figure out how to get from immediate random admin type job to ‘actual job you want.’
So you need an immediate plan, a mid term plan and a long term plan.
Agencies - pick several. Look at the types of jobs they offer. Sit down with your CV and a cover letter and tailor it to the type of roles they offer. Go through a dozen or so job listings and note/highlight the key words they have in common (things like key skills, attributes etc.) then you need to make sure your CV and cover letter reflect that you can offer what they want. So maybe an office admin job needs software x y and z, personable manner, phone skills, filing, diary management etc. All those need to be in that cv and letter. Think of each job ad as a lock and key - you need to be showing in your cv how you fit their role and can benefit them as a company. Far too many people have a general list type CV that’s just them listing their achievements. A hirer is looking for ‘how can this person help us?’ NOT ‘oh they’ve done well’
Every job needs a tailored CV and cover letter. Spend time on it. Talk to people. Go into the agency in person - be polite, well presented and positive.
If you want to be a writer - then write. The writers I know wrote, and still write, constantly. What they didn’t do was initially get a job writing - they all did it around other jobs, in evenings and weekends, small bits here and there and built up.