It's perfectly possible to play for free. At the start, you will get some boost out of cents, but its not a significant one. Once you reach certain point in the game, the only things you find useful are teleporters, and combat/hero buffs.

Instead of teleporters you can use jump cities or cap lvl10s from distance. Excaliburs, corselets, horns etc are not necessary for any battle, you will just face slightly higher losses.