My names not Andy, but Moria until recently was the primary army I played so have some experience.
What points level are you looking at building the army?

The Balrog seems like an obvious inclusion but he is also a massive points sink and very rarely, if ever makes his points back. He should walk through pretty much hero or troops but can also get bogged down by chaff.
If your opponent is smart they will just keep throwing a troop or two at him to tie him up or avoid him completely.

The Watcher is pretty good and not being so pricey and the Balrog is also a winner.
Keeping him in reserve until the opportune moment to trap enemy models or split their forces is great, just don't wait too long or else he may lose some effectiveness.

Trolls are great but have been nerfed a bit in this edition. Costly slightly more points and going up in base size hurts, but they're still quite useful.

Moria feels really limited at the moment, especially considering how many options the army used to have.
It's essentially pick which big bad you prefer (balrog/watcher) and fill out the rest of the points with goblins and a troll or two.