So I don't know much about Extended but here's a deck proposal revolving around Chandra Ablaze:

Her mana cost is pretty high but all her abilities are pretty damn nice and her ultimate should win you the game. Also red has plenty of mana-accelerants still available in extended. Here's a rough list designed to get her out fast and do some major damage. I have no idea if this is good or not.
Lands: 18
16 Mountain
2 Spinerock Knoll
Planeswalkers:2
2 Chandra Ablaze
Instants/sorceries: 18
4 Rite of Flame (Mana Accel.)
4 Lightning Bolt
3 Browbeat (The best I could do for card draw while keeping this mono red)
2 Manamorphose (see above)
4 Lava Spike
2 Magma Jet (Library Manipulation)
2 Empty the Warrens (Alternate win-con if ultimate is activated)
Sideboard:
3 Pithing Needle (for relic)
2 Dragonstorm (alternate win-con)
4 Bogarden Hellkite
4 Ingot Chewer (for Chalice/dredge)
2 Volcanic Fallout (against aggro)
So is this a good start? I thought Chandra's abilities were too great not to pass up. Let me know what you think.