Facebook ads can work but it doesn't mean they always do. I've seen, as my products are targeted to a specific geographic region in the US, that there can be a lot of success with running a geo-targeted Facebook campaign for a short period of time.
Daily budget depends on your audience size. Since my audience size is specific to one region of the country my budgets are much smaller than a national campaign. If your budgets are fairly small then try to add more targeting to reduce the audience size (age, interests, topics, etc.).
CPC or CPM depend on your goal. Looking for people to engage with your site? Typically CPC works better as Facebook will then optimize for quality engagements. Looking to just gain awareness and have as many people as possible see your brand? Typically CPM works better. However, test each one before fully commiting as these typical situations are by no means the rule.
And, finally, choose the duration of your campaign strategically. I've found that if running a campaign for longer than a few days I'll see deminishing returns after the first couple days. Facebook will keep showing ads to the same people again and again, which isn't always bad, but then these impressions are less likely to gain new clicks and ultimately conversions. I try to run campaigns for a couple days and then start a new campaign rather than keep the same campaign running for a long period of time.
Hope this helps!