Hi,
1 CPU and 1 GB or RAM is without a doubt too little to run OpenVidu Server, as you have already discovered. Try the 2 CPU 2 GB droplet. Recommended especifications ar at least 2 CPUs (if not too many streams are expected at once) and 8 GB of RAM. So RAM could be a problem here. But if you were able to at least launch the service with only 1GB, maybe that will be enough for you.
If CPU is reaching 100%, then you won’t have other option but to increase the number of CPUs of your server.
Regards.