You don't need a beer thief if you are fermenting in a bucket. When you need to take a sample, just take the lid off and use a sanitized measuring cup, ladle etc.
For a timeline, just leave it for 2 weeks or so before you start testing gravity. An important thing to know is that beer doesn't like to be rushed, but it doesn't mind waiting. You can let it sit in that fermenter for months and it will be fine.