Broodmother is a bit of a weird hero right now because she's extremely powerful early game but becomes quite weak in the mid and late game. To add to that, she gets quite countered by AOE's, stuns, and a fairly large handful of heroes.
This game is maybe not the best example of this because my team did some failing and lost to a super greedy lineup, but I think I properly demonstrated the early game.
In the mid to late game, aim for Manta, Black King Bar, and afterwards some carry items like Abyssal and Butterfly.
In the early game do your best to harass heroes, create pressure on the map, and give space to the rest of your team.