More of the theory-crafting article
here and a video which I haven't watched, but appropriately titled
"A beginners guide to deck-building"
As a general rule, you want probably 25-30 creatures in your deck. There are always exceptions, but a standard deck to be competitive would be around this number.
Scrolls I would consider MVPs from each faction would be :
Growth :
Kinfolk Brave : Early board presence and attacking each turn
Kinfolk Veteran : Haste is an outstanding effect and will get you out of trouble many times
Stag Heart : The Stag Heart buffs compound and help create some nasty nasty units
Wetland Ranger : Attacking each turn and buffing other units attacks if it hits an idol.
Order :
Aging Knight : Early board presence
Reloras, Lord Knight : Unique, so only allowed one of the field, but buffs this guy offers are amazing, especially to relentless units.
Royal Skirmisher : Relentless, nuff said.
Ducal Skirmisher : As above, but even better.
Energy :
Dust Runner : Early presence and being able to snipe 3hp units
Hired Smuggler : Early presence and the sweet sweet draw
Burn : No energy deck ever would be without this
Violent Dispersal : Violent Removal, though actually on the fence about this, I think I'd prefer Automata Forge, but couldn't make up my mind.
Decay :
Harvester : Probably my favourite unit, just scary
Rot Eater : Left unchecked, this beast will just grow and grow
Soul Steal : For killing Kinfolk Braves, Aging Knights, Dust Runners and Hired Smugglers
Necrogeddon : Wins you games.