First thing's first - stop leveling anyone else at all other than food. You've already wasted too many resources on sub-par champs.
Second - stop using resources on non-level 60 champs, period. Doesn't matter how good they may seem. Don't do it. Only ascend/book/mastery level 60 champs.
Lastly - for now your priority is to build a Dragon team. Dhukk is a solid choice for a debuffer, and Skullcrusher is also a good choice for the team - but things fall off pretty sharply from there. Get Fayne to 60, she'll be your boss killer. You're sorely lacking on support champs though, which means, for now, DO NOTHING ELSE but level food! Stop wasting time doing anything else, and wait until you get some better support champs.
That's terrible advice for multiple reasons. First, no, you do not need to spend any money at all on the game. You can progress just fine without ever spending a dime. Second, if you are going to spend money, using those shards at any random time like right now, is a terrible idea - you should absolutely only use them when you are able to complete a fusion with them. And lastly, wasting resources on useless champs instead of on food is a great way to put yourself into a self-defeating cycle that ends in trolling the forums with bad advice.