Medallions are cheaper and occupy a much more important slot on your curve
But in general, running out of spells is the best way to lose at Limited so, as odd as it sounds, I would regard Clattering Augur, Echoing Return, Gilt-Blade Prowler and Greed as perhaps the most indispensable cards for this archetype if you arent splashing
Dark Ritual is the big problem with Bargain decks, as it gives you the mana needed to play Yawgmoths Bargain well ahead of time
For one Green mana, level 2 helps protect your team as long as they have a +1/+1 counter
If youre on an aggro plan, you might consider the efficiency of White Orchid Phantom as an early disruptor that can turn a powerful land into an innocuous basic land, making it one of my favorite newer cards
This, alongside a mana neutral rock like The Great Henge, can create infinite colorless mana