Basically, for startup marketing which is 0 to 1, you need someone with no baggage i.e. who says we should only do organic or only do email marketing because they have seen it working at their last job. You need someone who can unlearn what they think works and experiment all their assumptions again, and has a fair bit of skill in different channels, a strong generalist, find someone who has done it before.
Another trait to look for is how they make decisions. Do they find out the "truth" from how competitors are doing it or are they willing to go the extra mile and really find the truth about the marketing/positioning from primary user research. If you get stuck with a non-original thinker, you would get stuck with someone who looks upto your competition to build their strategy. Not ideal for a first hire.
Lastly, healthy impatience in whatever they do. When time and money is limited, you can't sit on your chair waiting to get answers, you should be proactive and impatient in seeking insights. Underrated skill.