Before signing up to a casino you should look what are the available promotions for new users. If there is none, check for reviews sites for that same casino, because maybe there are benefits if you sign up through a referral link from a partner of them or from common users in general.

Sometimes casinos do this to incentivize more people to promote their platforms, so a middleman (referrer) is needed in order to acquire the bonus for yourself, as a newbie.

But don't focus only on sign up bonus. Follow the social medias and official threads of casinos on this forum to know when they launch bonus, promotions and giveaways, so you don't miss any opportunities.