You are the controller when it comes to Facebook Ads Cost. Facebook gives the ultimate option to control the overall budget. You can control on a daily basis and you can control it as a lifetime budget too.
The things you need to understand is your objective of this campaign, for example, awareness of your brand is your objective or showcase the offer, or get more traffic to your website. Once the objective of the campaign is clear you can start your Facebook campaign.
Sometimes you need to contact an expert for the campaign where the goal is more specific.