Depends what your short term goals are. Arena, CB, Dungeons?

At some point you will most likely 6* Apo, Steelskull, Roshcard, MM, Fu Shan, Lua probably, maybe Seeker, maybe Vrask. Those champs range from top to very good overall or good for specific content. 

The question is where you want to make the most tangible progress in the next few weeks. 

I need some for dungeons. Do I need faster faming, now is on about 30 - 40 sec?

I wouldn't worry about faster farming than 30 seconds. Apo is great everywhere, imagine you will be using him at 60 everywhere. Definitely start doing 60s and no more 50s. My recommendation is to pick those that are most versatile first but also fit into late stage as well. 

@Trip has a point. Shortening your farm time now will not be as beneficial for you as any noticeable progress in dungeons. Later on you will replace Kael with better farmer for sure, but that will happen naturally when you progress and continue to acquire different (and hopefully) better champions.

At this point maybe Apo or MM may be your best overall choice. Now your Royal Guard may seems really strong to you (and he is in term of damage output) but he will need some babysitting when you start to dive into dungeons. Both of these can help you clear waves and support you damage dealers Kael and RG, they can be used in your short term CB team and in Arena, till you start to work on your better existing one.

MM is one bad mother@r and I really think of him as disguised Legendary champion. Apo, though sometimes his AI may seems inconsistent (always priorities his speed buff, even someone in your team is about to die) is one of the best rares with his short cooldawns for speed buff and flash heal.

Then, when you start to worry about your Arena, you will want to build your Seeker, Roshcard, Fu Shan; when it comes to CB, you will want that green beauty, called Steelskull (you will definitely need books and correct mastery on this one).

CanOfBliss said:

I agree you're eventually going to 6* Apo at some point. I would recommend Galek or Athel right now. It's really up to opinion personally. You can make some amazing builds with all different kinds of champions, But I've seen a LOT of power come out of Galek at least.  

Galek or Athel, provided he has so much better characters than both of them when it comes to single or AoE target damage, utilities and/or general usefulness?

With all due respect, but I politely and firmly disagree.

Tnx guys, I did Apo first. My next will be MM. Except I got some beter champ i neer future. With my luck i dont think so. :D I appreciate your help

Good choice, I think apo then MM is best route. Especially since you can book apo easier. I wish I had MM.