Whenever you are running a new ad campaign I would recommend you go through and AB test all of your options. I wouldn't suggest focusing on manually placing a bid though.

Facebook is extremely effective, a lot more than people realize & a lot more than Facebook advertises. Using their "optimize my bid for _________" will make sure that you are getting the most out of your money. If you are manually placing a bid you wont be able to figure out how far you can scale your ad which is a real pain for testing.

Instead of struggling to get Facebook to accept your $0.20 bid I would spend more of my efforts AB testing demographics, interests, copy, & images trying to find optimized ads that convert closer to $0.10 CPC.

If you have any more questions on this feel free to just shoot me a message or schedule a call. If you're spending any decent amount of money on Facebook ads it will probably be worth your time to have a professional manage them or at least talk with one before you set up your campaign.