Hi Reth, welcome to Redemption!
I am still fairly new myself, so hopefully other people will expand upon my post, but here are a few tips & suggestions regarding your questions:
- There are many themes and concepts that you can choose from to make your offense and defense, and mostly the same theme will be in the same brigade (blue - Egyptians, purple - Kings or disciples, orange - demons, silver - angels, etc). That being said, it's fun and useful to "splash" together a few different brigades of cards that work well together...I just would advise not having more than 3 different brigades for your offense or defense - you'll want to look at your enhancements and see what's reasonable. The danger of having too many brigades is not drawing characters to match enhancements that you have drawn, or vice-versa, leaving you unable to play offense or defense for possibly multiple turns in a row while you wait to get your needed matching card.
Some artifacts are worth using, even if they hurt your offense or defense, because you figure it into your strategy that it will (hopefully) hurt your opponent more than you. Covenant of Death, for example, negates all characters including your own, but it might be your strategy that you will have a lot of characters with abilities that cannot be negated. It all really just depends on your strategy.
Finally, I really encourage you to have fun with the decks you build! I like to make decks based off of my favorite characters or events from the Bible- it's really fun!
Blessings!