It depends on your needs really. DO is fine for low budget projects. Just below them I would suggest Vultr. If you don't care about API's and that sort of thing, then Ramnode is even cheaper, but I've had issues with the user interface.
There are a bunch of aggregator sites that compare vps providers. Here are two of them. [1] [2] [3]
Disclaimer: These sites can be a bit spammy. Use NoScript / uBlock. Also, you really do get what you pay for, so as your business grows, you may wish to consider diversifying across providers.
[1] - https://lowendbox.com/
[2] - https://vpscomp.com/servers
[3] - https://www.serverhunter.com as mentioned by
IronBacon, I totally forgot about this one.