Choosing a Facebook budget depends on many factors which are nearly impossible to calculate in advance.
Successfully converting views to clicks to customers heavily depends on your ad, your messaging, and your web page. This is why I suggest starting fast and small, capturing enough data in a brief period to be able to better make this calculation.
Let me explain.
If you throw $1,000 on a single ad over a period of a month, you'll be spending $30+ a day for a few days while you figure out if your ad is working (or not). Instead, why not create a test ad with a small budget, run it for a few days, look at the results and tweak things a bit?
If instead of coming up with a massive budget up front, you create an ad that runs for three days for $5 a day, you will have enough data to figure out if your ad is effective.
The main thing you'll want to track is your conversion cost. If you can convert a customer for less than $3 on average, you're off to a good start. Of course, you want to get this number as low as possible, but anything under $3 is enough to promote a bigger ad for a longer period (especially if your product is on the more expensive side).
If your ad runs for three days (and $15 total) and has a conversion cost of $10, you'll want to adjust your ad and run it again using the same formula... 3 days, $5/day. Each time you do, check your conversion cost and decide if you're ready to go big.
Once you have a high-performing ad that converts to customers for a predictable and low cost, it will be easy to calculate a budget.
Take care not to run the ad for too long... people get used to seeing your ad and grow insensitive to it, and so at some point ignore it. When this happens, you'll see your conversion rate drop, and you'll want to change your ad a bit or start from scratch.
Now that you know how to budget, read How Do I Advertise My Business? and What Are Some Tips to Making Effective Facebook Ads? to get some pro tips on creating an effective ad and publishing it on Facebook.