If you only start with the first 2 lines of masteries you do not need to be too picky, it takes 100 scrolls which you can hit the Minotaur up for. You can visit ayumilove.net to get a sample scheme to use.

But if you are serious about getting the whole 9 yards, that will take 800 gems per champ, and you need them fully ascended.

Often the schemes will present different scenarios of arrangement based on intended use.

But be careful, correcting mistakes (you get one free redo) can be costly.

Scyl is amazing for just about any dungeon content... really considering she is free she is brill.

I do see her sometimes in arena but i dont really worry about her in arena.

Tormin - everyone with a speed nuke team in arena hates tormin (i do anyway).

For masteries i would use the guides for an idea, but dont be afraid to deviate.

https://ayumilove.net/raid-shadow-legends-scyl-of-the-drakes-skill-mastery-equip-guide/

https://ayumilove.net/raid-shadow-legends-tormin-the-cold-skill-mastery-equip-guide/

Hey guys,  THANKS for this link.  I beleive it will be very helpful to me.

Definitely Scyle as suggested previously. Also word of advice : check the videos ( as many as you can ) befor echosing masteries, as the ones featured in the site are ok for general purposes but you could always find better ones to fit your specific teams. 

Tormin too is a great candidate as even if he's mostly used only in arena he can also be a great carry in dungeons, DT and Faction wars.