Harem is a messy business in and of itself. The wrong misconceptions people have is that there could be a possibility of a happy go lucky family of harem.... Ssk ssk ssk.
You want a proper harem? Read through historical references, learn what the culture around them are. How it isn't actually anything about romance or snu snu, it's simply plain old politics. This tribe is located quite far from control, if it falls into the enemy hands that could let them build strongholds...so? Go bring that tribe chief's daughter.
They didn't even have to consummate it sometimes, just the alliance was enough for most tyrants.
The harem court isn't one of girls giggling and having a merry time cherishing their emperor's dong, it's one of brutal power struggle. Concubines scheme against one and another, the empress or wife poisons or makes others unable to sire children, etc...
You want to write harem? Then forget about fluffy, forget about making it a romcom, there's no love involved here. Sure you can write tapestry of how much of an ardent lover the mc is to all his "wives" but at the end of the day, it will be shallow as he is a human after all and won't be able to be with all of them. The old ones will get sidelined and the whole "she is the love of my life" shit just becomes hypocritical.
Make it a power move. Have instances of intimacy and laughter, not everlasting love. Have fights and deaths, have schemes and betrayals.
Ofcourse you could just take the fast food route and just pop out new jade beauties each region and forget about the old ones. If you do happen to remember them thousand chapters later just mention in the passing how devotedly they had been waiting for them for 500 years without even having thoughts about moving on, and without leaving the house or having a life all the while not even a reaction to the constant adultery of mc around the world.