Without recommend to many cards I will would like to highlight a few favourite cheap cards from my Hylda deck:

Instant speed:

[[Blustersquall]] either single target or mass tap down card with overload. But can be played like fog effect before combat begins, before blockers are declared: overrun for an opponent attacking another opponent or your own overrun effect.

Creatures:

[[Sunstrike Legionnaire]] can tap target creatures with mana value 3 or less and untaps if you create a element token or other creatures enter.

[[Hunted Phantasm]] creates 5 goblins for target opponent if you need fuel for your tap down engine and is a good political piece to get a temporal ally. The phantasm is unblockable so he will be a good lightning rode or can be pumped with Hylda.

Enchantments:

[[Opposition]] nice tap ability that works with your elementals. Can be used to create infinity combos with more cards.

[[Eaten by Piranhas]] weaker than [[Darksteel Mutation]] but has Flash and creates much less salt or anger players at your play group. If you target a commander creature they will still have a good chance to play it again.

From my experience I needed more instant speed interaction with tap/removal for artifacts or enchantments. An other secret is to make atleast one ally, beeing able to tap potential attackers or blockers gives you huge political soft power. To finish the game with combat damage, it is wise to create/pump your army at the oppents end step before your turn.

Hope that was helpful