Can You Share some experiences about your tech blog?

Actually, I'm a local SEO guy, working for my clients. But recently I have created a new blog on the tech niche. My plan is to write on mobile cases, upcoming mobiles, and gadgets. Can you share me some tips that will help me to bring maximum results?

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1. Should I have a super single topic? (like only phone cases, or maybe only iPhone cases)
2. Should I publish daily content?
3. Should I write long content or 500 - 700 words enough?
4. How long it will take to see some good results

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I highly appreciate your tips, please share your experiences or opinions.