I've played Division 2 since release. The nice thing about the game is that literally any kind of build works for Solo play till end-game. Even with the expansions. The only time "Builds" are required is if you're doing Darkzone or the raids.
An easy way is just get the Aerial Drone and the Roller Mine. You'll find some mods for the Roller Drone that increases how many little bombs it spits out, and you can find some good mods for the Drone that increases it's damage like 270%. That shit will clean out entire rooms of enemies.