How to thank someone who referred me for a job?

Hi all, I have a general question related to a post-referral situation.
I'd like to know what's the common ways/levels of showing gratitude to a person who referred you for a new job.

Some story:

You have been dissatisfied with your current job, so was looking for another job but haven't been quite successful for a while.

Someone that you've met from a conference told you about an opportunity in their workplace. You only met this person twice in the past, and you haven't talked to this person outside the conference sites.

You showed your interest, the person referred you via their hiring system, and after some interviews you finally got the job.

It's a well-known and big company, while your previous jobs were at much smaller and local companies. So it's a big step for your career and you will definitely get lots of benefits from joining here. Without the referral the chance of you getting the job is fairly thinner.

How would you express your gratitude to this person? What is usually okay and what's usually considered too much?

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