you rang m'lord
where are you from kiriz?
legally - you need a visa to work in ibiza. if you are an EU citizen then you don't, but everyone needs an NIE to work, which aside from being legal gives you basic protection under employer's liability insurance/employment law, etc
illegally - many people work in ibiza without papers, they work cash in hand and clearly run the risk of being treated badly or poorly particularly in relation to wages and payment.
in the last few years, i think there has been an increase in the requirement for an NIE amongst employers and you cannot obtain an NIE without a pre-contract from a prospective employer.
having said all that, i worked in ibiza for 3 years (summers) without papers and it never affected me and friends have worked there in the last couple of
years and just worked without an NIE.
i'm sure if you "know to do a lot of stuff

& feeling crazy to come 2 ibiza" then everything will be fine, but be careful.