Forget about hydra for the moment, the first thing you need to focus on is getting gear from dungeons.

Take ninja to 60, he's good for pretty much everywhere. Mordecai will be very good for regular dungeon spider.

Deacon, Steelskull, Magnarr and Apoth are all worth taking to 60.

Where are you on dragon?

Your immediate goals should be to get to grinding dragon 20, spider 20, and campaign 12-3 brutal.

Thanks for replying. I'm stuck on dragon 18 and 14 on fire knight. 

I don't use my ninja much other than tag team arena, he's pretty hard to keep alive, i think I have him in the wrong gear. He's in full 6* epic and legendary slayer gear. 

I am still figuring out how to put together champs for specific team roles that work together. 

I am on nightmare in campaign stuck on 8.3 valdimr . 

Ninja is squishy, that's pretty much his only downside.

The important vital thing to know about gear is stats matter way more than sets. A 6* legendary piece that has terrible stats is a terrible piece.

I'd suggest ignoring NM campaign for now, The difficulty ramp up is nuts, and there's no real benefit to working on it until you can complete it.

What I'd work on first thing is get those champs I mentioned to 60, and get them full scrolled in minotaur. You are WAY better off to do minotaur runs instead of just buying the scrolls with gems; just buying energy potions with gems works out cheaper, but you also earn xp and silver.

For spider; the main strategy is to use aoe burn, then reduce big spider's turn meter and let the burns do all the damage. So mordecai sets everyone on fire, Armigar (make sure he has 100% crit rate) only ever uses a1, and hits spider. Soulbound bowyer also has tm redux, and could be useful there

Fk is all about multi-hits to get his shield down. Apoth is actually really good for that. Rhazin is too.

Three things. First, you can sort the champions horizontal to fit more on the screen (for future reference). 

Second, Moored is right about not worrying about Hydra for now and getting Ninja 60 and built. However, with Ninja you also might be able to get the lowest chest on Normal Hydra before your team dies. That would be worth doing since you'll get Mithrala Fragments that way, even with the bottom chest. 1.7 Million damage isn't too hard with his HP Burns especially if you bring Mordecai.

Lastly, Moored is also right about Apothecary for FK. Based on who you have, here's what I'd do for a FK Team:

Ninja, Apothecary, Gwyndolin, Deacon and Lanakis. Ninja A3 at the start of each round to freeze everyone, Gwyndolin for the AOE Decrease speed, Lanakis, Deacon and Apothecary get you more turns to kill waves plus Increase Attack and Decrease Defense.

Then just make sure you have Lanakis's A2 ready for the start of FK's Round. That teamup will likely bring down the shield immediately. 

Gwyndolin's A1 hits 3 times AND she gets Extra Turns sometimes. The only issue is going to be survival. You can try Riho instead of Deacon, the waves will take longer but you'll have more survival against the boss.