I believe that adding more people to your team needs to follow the needs of the business. This means making sure you can break down the goals or OKRs that you, as a PMM leader, is responsible for and outlining the key initiatives that will help you achieve them. Part of this exercise is to also identify what you can and what you cannot do with the current team. For example, you may list out things such as "create competitor battle cards, conduct win/loss analysis, write 3 new whitepapers, implement a new campaign strategy". Great, you have all of these key initiatives that you have connected with key business goals. Now, who on your team will do that? If you only have one person reporting to you, there's only so much you two can do. The next step then is to explicitly call out what you will NOT be able to do. A good idea is to put your plan on a page with items that are your high priority and items that fall "below the line", i.e. not enough resources to execute.
As you share this with your boss and the rest of the executive team at your company, one of two things will happen. You will either be told OK, we understand there are things you won't be able to do and we don't have the budget to get you more help; or you will then be told OK, we see that you need more people to help execute!
So getting back to the question about scaling the team, I believe that if you are able to make a case for more resources and you get the budget to hire one, two, three, or more people for your team you gotta think about them in terms of what key priorities they will have so that you can look for the right skills to hire. Make sure that as your team scales your contribution to the business grows proportionally and you will be able to scale the right way.