Are there better ways to increase troop size?

I’m at the point where upgrading the Drill Grounds is not worth the effort anymore.

Not only does this take several days if not a week to complete but the addition after that is close to nothing (I only see another extra hundreds of units efter each additional level). Plus, the resource costs for leveling up your Drill Grounds beyond level 25 is insane.

So my question is: are there any better ways to increase the unit count or should I say the army size in Last War Survival? Thanks!