Be sure you understand and articulate *why* you're building out the team. We all want to grow the marketing team, but growing for the sake of growing can often cause more problems than it solves. To be effective at a small company with a small team, you need to grow strategically and focus on the most important initiatives.
Put together a list of projects you'd like to tackle and other marketing-related inititatives. Then talk with your stakeholders in product, sales, and customer success to see what they would like to see from marketing. Work with those stakeholders to prioritize your list. Then approach your manager or executive with a hiring proposal for the next 12-18 months that addresses those priorities (e.g.: hire a GTM-focused PMM in November to accomplish these sales enablement initiatives, a Creative Director in January to address these needs, etc.).
It makes sense that the first marketing hire on a product-led organization is the Product Marketing lead :). I would say put your strategy together and depending on the priorities you will see what kind of marketing hires you need, vs perhaps going with external agencies for some marketing activities. You may want to keep the strategic items in-house like competitive intelligence, but anything related to marketing campaigns you could start with external agencies / contractors with the optionf or them to become full-time. It really depends on your audience and what you are trying to do next. For example, if you are targeting developers, my first hire there was a technical writer to clean up the product / API / SDK documentation. So sorry to say that the answer here is "it depends", but hopefully the context above can provide some pointers.
There are three capabilities you'll want to be sure are covered in forming a modern PLG marketing team. This is my take on their order: