You can use HAProxy for load balancing, there are articles about it here:
With a single HAProxy node, this woulds still leave a single point of failure. Since DO doesn't support floating IPs (yet) you can't scale this up to having 2 geodiverse HAProxy nodes. That said, it's still an improvement over round robin since an app node is far more likely to go down than a slim, hardened HAProxy node.
You can also use nginx for load balancing (this is quite popular these days):
nginx will have the same issue that HAProxy does, in that you still have a single point of failure.
Since DO doesn't support floating IPs (yet), I'll mention Amazon's Route 53 which is capable of intelligent round robin, health checking destination nodes, and geo-diverse hosted DNS, it's also relatively cheap:
You can use Route 53 in conjunction with DO droplets. I believe DO is working on their own implementation of floating IPs to solve the super high availability problem.
This article covers how to set up a simple load balancer on a DigitalOcean droplet with nginx. The tutorial covers setting up a round robin loadbalancer that can then direct site visitors to one of a set of IPs