You can but 1 day my shop passes which are cheaper (or get them from FUN scratches, low drop rate), but honestly I feel that premium is worth it.I'll probably start by purchasing the inventory upgrades. After that, once I start getting drops I can make money off of, I'll consider the premium. It seems like it will be super helpful when leveling subclasses.
I also strongly recommend getting daily login onuses in PSO2es - the app can also be used to feed your mag and pets, so you can level them faster.
You can even check the status of your myshop items and collect money for stuff that was sold.