Invest a good amount of money in designs.
To distinguish them from the rest of the market go for an over arching theme (ideally based on your company name) and get them done in an easy to recognize style that isn't generic Anime, if possible get them all done by the same artist. This will help your company develop a "brand" and feel, and it'll help distinguish you from Holo, Niji, and the other small companies. You can't compete with Holo and Niji directly, so don't even try.
In terms of management, just make sure your girls stream regularly, slap them on the wrist if they do something stupid or something that could sully the name of the brand, but apart from that try to be hands off. Encourage collabs, try and create a good group dynamic between them.
Everything from here is down to the girls you hired and luck. Maybe hire clippers or anitubers to shill you, or buy some advertising space before debut, but apart from that you just sort of have to pray things work.
