Army-Box

Personally, I think it is a great core for an army. Asphyxious the Hellbringer is a really good caster, the cankerworm is one of the best character jacks out there, the slayer chasis, while getting a lot of hate, is cheap and a good filler. With the battlebox and the all in one, you have enough arc nodes for most casters. Bane warriors and darragh are both solid purchases in my opinion. Weapon masters that hit like trucks and Darragh is a tool box of versatility.

Depends on your play style and what you like.

Satyxis raiders are definitely worth the purchase, though currently do not fit into any theme forces. For their points, they can hit hard enough, jam hard, clear out infantry, and be resistant to shooting.

If you want to do ghost fleet, that would require significant resources to purchase a lot of the revenant crew and possibly black banes. Not a beginner list.

Jack wise - I would recommend one of the crab jack chassis. I love my harrower, probably my favorite non-character, non-colossal jack, and I think it got an upgrade with Mark III, but a reach heavy with thresher and ways to boost accuracy can really do some damage.

Character jack wise - I love the deathjack even though he took a hit in Mark III cost wise and functionality wise (with the hit to necromancy and the soul thing), he is still our hardest hitting non-colossal warjack, advance deploys, can cast some spells and has a max focus of 5, 2 of which it gives itself. An argument can be made for barathrum as the best character jack for the points, I just like deathjacks model better.

Solos - I am a big fan of pistol wraiths, war witch sirens, and if you do decide to go satyxis, get the captain. auto knockdown on a solo with high stats is really good. If you go banes, tartarus is a good buy. Not as good as he used to be, but still worth it if the changes I heard from the CID go through (free in theme, reduced cost otherwise).

So in all, you have a good core already. Play with what you have, see what you think you need and fill in from there. If you need better infantry clearing, satyxis or perhaps bile thralls or bloat thralls would be good. If you need armor cracking, a kraken or deathjack may be good. If you need good scenario pieces, go something incorporeal or a jamming unit. If you need focus efficiency, look for the withershadow combine or the deathjack. See what holes you have after playing and fill from there.