What To Do With Low Mana in Soulkeep?

What could you do with Fiends that are fierce and going to your gate and at the same time you don't have much mana and you have to defend the whole map so you could stop these fiends from going to the gate and cost you more hearts and this is the point here.

When you have low mana first option to think about is common towers as in this case rare and epic towers would be so expensive to use and you wouldn't have such ability to use these towers as least one is more than 100 Mana.

Even some common towers couldn't be used as you are to use a towers that less than 100 Mana and these are such Card Sharp and also fountain of terror and this is a two towers to use for moderate mana to be used.

For less mana you could use Tarantula Loom with only 50 Mana and Gloom owl with 60 Mana and also use Knife Trosser for only 55 Mana and also you could use a spell like cheapo for more mana discount and you couldn't use Mana Mania as you are in first wave and you have to start with good deck before you could accumulate mana.