How do I know how good a fiverr SEO expert is?

Hey everyone,

Im new to SEO and had a couple of questions I'm seeking answers to:

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1. How do I know how good a fiverr expert is? I am narrowing down the ones with about 200 reviews.
2. Everyone seems to be offering keyword research and competitor analysis. How can I make sure the person i hire is doing the best job for me? Are specialists demanding higher pay capable of doing better keyword research?
3. If i am drop-servicing SEO, what is the price band within which i can charge it to my client? What's the highest and lowest?

Thank you!