RE: Warning: Some bots are not giving good vote even it says ROI: 10%, a method to learn if a bot is good or not

I use steemnow but multiply the SP by 100 to have accuracy as it avoid roundings:
Screen Shot 2018-05-25 at 11.12.05 pm.png

For example here, with 15450 SP you get a $3 upvote. So for $0.03 you need 154.50 SP.

You can also simulate SP with this great tool:

That big circle on the top left with your vote power inside, you can click on the outter ring to show you the vote value at different vote powers. https://steemworld.org/@hungrybanana

There is a Simulate SP button on the right.

You currently have 226.43 SP which gives you $0.04 upvote at 100% weight.