FIRST
You must get skilled job with company in the UK.
They will send you letter which you use to get working visa.
JOB comes FIRST then VISA
you will not get working visa to come and hunt for job or hussle.

emma even if you get the work in uk your employer has to prove beyond reasonable douth that there is no other peeps in uk that are available to do that job,

they have thousands of people in uk out of job and you as a naija say u get a job offer, abeg my bro/sis leave that one make u find beta tin do

you can maybe try your luck on study visa

Go and read this;
http://www.ukba.homeoffice.gov.uk/workingintheuk/

Gives you very comprehensive insight on possible routes to secure entry to work in the UK and do not forget to read the APPROPRIATE PBS policy guidance (a separate document which you will find also on that link)word for word if you are considering a route that falls under the Point Based System, (PBS).

If still confused, then come back with specific questions and we will gladly assist you.