Hi and welcome,
You can certainly make a start. There isn’t a testnet running right now, but we can expect testnet 3 soon - guess < 1 month.
I suggest starting by building according to the instructions, reading up (How to build an App on SAFE Network should get you started) and ask for info/help here.
As I understand things you have two main choices: the REST API or using shared file system / Drive (see link above). I’m not 100% sure but hopefully we can work it out without distracting the devs too much!