Creamsteak
Explorer
Let us get to the heart of the question of why you selected the bard class in the first place. What is it about that bard class in particular that appeals to you for this character? Would you consider another class as an alternative if it fits the character better? (Any class could have the entertainer background and still fit your description quite well.) I suggest taking a look at page 52 of the PH under "Creating a Bard" and thinking about how the character became a bard in the first place to help answer these questions.
I was debating between bard, ranger, and cleric mostly. I also considered rogue, but she's just not smart enough to be the rogue I want to play. She's witty and creative, but not brilliant. I also was a little inspired by Lindsey Stirling as I worked through the concept. The bad gambler/cards concept has to do with fate and luck. I was more imagining a first level character as a "talented commoner who turns to adventure" instead of someone that already is an adventurer. When you ask how she became a bard, my mind immediately went to admiring some older gentleman bard as a kid growing up. She might always have been aspiring to find this person who was kind to her and who, to her, performed the most amazing performances. Perhaps he gave her the first instrument, and she thought the world of this gentleman as a child. But he, like everyone else in her life, left and moved on.
I think an entertainer/gambler hybrid background would make sense. How about something like:
Entertainer Routine: Singer
Personality Trait: I'm a hopeless romantic, always searching for that "special someone."
Ideal: I like seeing the smiles on people's faces when I perform. That's all that matters.
Bond: I will do anything for the poor, the meek, and the downtrodden.
Flaw: I am a gambler, but never tell me the odds.
With skill proficiency with the Viol and Playing Cards. No dice.
Perhaps she could use the usual bard performance of viol and song in her spells, but when an inconsequential material component is required she burns a card instead of a duck's feather or whatever is specific. It could also be influenced by her spell selection. I was looking at a pretty simple set of something like:
Cantrips: Light, True Strike
1st Level [2 Slots]: Comprehend Languages, Cure Wounds, Heroism, Identify