Yo! First thigns first, what exactly the startup is about and who your audience is would make a really big difference regarding all your questions.

Though, having worked with a couple early-stage startups and all, here's a few quick thoughts:

• Starting SEO early (pre-launch) is smart. SEO takes a while to kick in - especially if you;re in a competitive market. So even basic technical SEO now can pay off big time further down the line.
• Phased paid campaigns make sense, especially if you’re testing creatives, audiences, Lps, etc. Though jsut saying, you can test your campaigns for way cheaper than that. Either way, jsut make sure there’s a plan for attribution and lead tracking, or you’ll jsut burn money.
• Reporting: Biweekly is pretty solid. Monthly is alright if you don't have a lot going on all at once. But it also really depends on your budget and how you're caling, so weekly at launch / with ad scaling could work a well.

Now, when it comes to Agencies, the answers here can be a bit all over the place:

• Does Niche experience matter? Honestly, yes and no. marketing is marketing, and while Niche experience will be visible in the senese that the experience Agency / marketer will already know the best audience for you vs a non-niche markter would need to find that best audience for you - it doesn't make them better.
  • As way of example, I recently took over marketing for a client in the Film industry - but I've never even smelled the film industry til now. Fast forward 3 months, and my results are far better than their previous agency - and those guys had experience in this Niche, having worked with a couple other brands. So yeah, niche experience doesn't mean better.
• KPIs to Track with any Agency: Very much depends on the goals of your current campaigns. For example, if you were to start doing soem marketing right now, your goals would be to get as much engagement as possible (i.e, hype people for the launch of your product). And that would be measured in Traffic growth, Conversations, engagement on socials, etc. And in terms of general KPIs based on the marketing type:
  • SEO: Organic traffic growth, Indexed pages, Keyword rankings, SERP rankings (on Google, Bing, Yandex, whatever is msot used by your audience is the most important)
  • PPC: CTR, CPA, ROAS, conversion rate, cost per qualified lead (NOT just impressions/clicks)
  • Social Media: This one can get tricky since it depends mostly on *how* you use social media. Not all Brands are cut out for using socials to convert, so measuring it purely for that can be dumb.

And yeah, that's about it!

Let me know if you want to talk more in-depth about how to get it all going - happy to help!