The basic ubuntu instance on DO is ok. SSH to the instance and:
sudo apt-get update
java -version
# should say "No java"sudo apt-get install default-jdk
sudo apt-get install screen
# keep server running when disconenctedmkdir minecraft
cd minecraft
wget -O minecraft_server.jar https://launcher.mojang.com/v1/objects/4d1826eebac84847c71a77f9349cc22afd0cf0a1/server.jar
# replace by the newest version