It depends on how interested you are in showing your ad. Did you choose automatic or manual bid? Either way, if you bid too low, there’s a risk that your campaign won’t get the right exposure and you might not reach your goals. If you bid a higher amount, you can always pay the lowest amount available in the auction in order to get your ads delivered.
Have you tried consulting Relevance Score metric that Facebook provides for each of your ads? If the relevance score of your ad is high, Facebook will show your ad more than ads with lower relevance scores, and, subsequently, you will pay less to reach more of your target audience.