Like every other marketing campaigns, budget is never too high or too low. You first being with minimum budget. I recommend $250/week($1000/month) and see how your are generating leads.
once leads start coming in and you start generating business, you can scale to 2k then 3k and so on.
Also, at one point, you will hit a ceiling where you can not spend more then certain budget, you get 100% impression share. That's your maximum budget. You can stop at that point.
Also, note that, your maximum budget through the year will change. Some months, you will have huge requirements. So, you will have to spend more. Some months, requirement will be less. So, you can reduce budget. Once you have run your ads for 3 to 5 years, you can see a pattern, and plan your budget accordingly.
