Agro red

Keeping in mind that this deck type is one of the ones I have the least experience with, I'd suggest the following:

You'd want some more 1-drops to speed up the deck as much as you can, cause you want to start the damage clock immediately. [[Flamekin Harbringer]] is a perfect fit in here. It doesn't net you any material, but it keeps the elemental count high, starts your damage clock, and sets up whatever critter you need next.

Convenient Target is a bit too slow and doesn't give enough benefit in the build as is. I'd recommend some basic burn like Lightning Bolt that you can use to remove threats or burn to the face to end the game instead.

Gnawing Crescendo has some cool synergy with the sac elementals, but the problem is, it costs 3, so to play it on the same turn as one of the sac elementals means you have to have 4, 5, or 6 mana available, which this deck doesn't want to have happen. It's also a dead draw in some cases, and really only gets value when you have at least 2 critters in play. As alternatives, you could go with the same idea of a broad boost like Painter's Studio // Defaced Gallery (it's a room card, you can get a LOT of value out of it in here), or play around with Risk Factor, which could also get some absolutely sick value in here, as you either refill your hand or get 4 damage at instant speed, then you can replay it from the grave later/then by tossing something you don't need, such as a land or target for Thunderkin Awakener. In fact, combined with Thunderkin Awakener, you could pay 3 for a jump-start Risk Factor, toss a Ball Lightning, get 4 damage or 3 more cards, attack with Awakener, and reanimate your Ball Lightning for the turn, which is either 11 damage or 7 damage and +2 material for the exchange. This works equally well with the other sec-elementals, which Risk Factor basically turns into free Lightning Bolts.

You can play around with your lands a bit too, as you're running mono-red so you don't need to get fancy but can still get some value out of the lands for cheap return. Castle Embereth, Contested War Zone, Shivan Gorge, and Barbarian Ring are worth considering in small numbers to augment 3 or so mountains, which helps cut down on the dead draws but still gets you what you want mana wise.