ive got a similar deck running at the moment.
except i went less creatures (2) and went for the pure burn.
what you need to pick up is the rare land for red. or 3 of them.
for comparison my deck is something like this.
1 rootbound crag
3 valakut, the molten pinnacle
4 seismic strikes
3 spire barrage
4 lightning bolt
4 burst lightning
2 punishing fire (want more but dont have)
2 pyromancer ascension
4 zektar shrine expedition
2 elemental appeal
2 magma phoenix
4 khalni heart expedition
3 expedition map
2 khalni gem
so basically it all revolves around getting to 5 mountains in play and at least 1 valakut out so then you can just spam mountains and lightning bolt everything. expedition maps help to pull the valakut out earlier, while khalni gems are great for being green mana for your harrows etc, whilst also bouncing mountains back to your hand in order to use them again with valakut.
pyromancer ascensions are ok, if you get one early they can be game winning, though you need to run a lot of duplicates to use it. The good thing is that harrow is affected by it, so this can be useful to get the counters on and also then be duplicated by it for masses of mountains. And when you manage to cast a kicked elemental appeal with ascension in play for 2 14/1 tramplers you will no doubt keep it around! Cheap burn is the way to go in the deck, and if you can find some magma phoenix they are brilliant. You will be winning the life exchange no doubt, so they can be quite effective as a stall card, in that if your opponent attacks they know it will block and die and inflict destruction on everything, plus you can always target them with your own lightning bolts to clear the board, and then buy it back with the masses of mana you will have in play. And the Zektar Shrine expeditions are great at getting a good life hit in early, for 2 mana and only 3 lands needed to activate it, you can pull it with a harrow 3rd turn for a 7 life hit.
hope that is some food for thought
edit: oh and due to the nature of the deck, you can probably get away with running less than 20 lands and still be effective. that being said I seem to have 19 anyway