Let’s say I just want one white PW to complete the Story Mode colour challenges. Which one would you suggest?
I’m not loaded with rares and mythics, so it should be decent with a cheap deck.
I finished everything with Gideon#1. It’s good at pumping below average creatures.
If I had to do it over again, I’d probably use the Serene Steward/Lone Rider combo with Nahiri or G1. With Always Watching and enough buff spells you could rip through most of the story battles I bet.
GIDEON basic. He’s an outstanding mid-high level PW with lots of deck potential. You can build very effective GIDEON decks with mostly uncommons. I have all 5 basic walkers and 3 dual-colors and Gideon is still one of my primary go-to decks.
Look at cards like: Consul’s Lieutenant, War Oracle, Serene Steward, Thalia’s Lieutenant, Relic Seeker, Hope Against Hope, Silverstrike for removal that bypasses Hexproof, Suppression Bonds and Swift Reckoning.
I agree with this. I also suggest Always Watching (not with Murder Investigation), Iroas’s Champion, Lone Rider/It That Rides as One, Murder Investigation (not with Always Watching), and Smite the Monstrous.
I have mixed feelings about Ondu Rising. Its good, but only if you can time it so you do not dump a bunch of mana into the Awaken end of it at a critical moment.
Thanks, I just put together a deck for Gideon using Serene Steward, Lone Rider, Nearheath Chaplain and Slayer’s Plate, to name a few key cards and it looks rather promising! 
I’m well over 90% win rate with it on QBs.
Lone Rider is a phenomenal new addition to white. He’s uncommon. He’s arguably better than War Oracle and Consul’s Lieutenant. He could replace either, but I kept both and swapped him in for Relic Seeker and the deck is significantly faster & stronger than before. With Serene Steward and 2 lifelinkers, the power grows very quickly and provides a lot of opportunity to recover even from deep deficits.
Finished the Origins Story with the deck and Gideon is still only lvl26
Grats. 
Thanks, I am quite surprised, actually.