This three-class combination is all about versatility. To really make this work, you’ll need a good Dexterity score, probably at least a decent Charisma score, and a decent Intelligence score as well. There’s not a whole lot of direct synergy on offer here, other than all three classes being really good at a number of different things individually and having an even more broad skill set when combined. Characters made with this combination are unlikely to be masters of combat or spellcasting, but will absolutely excel at social situations, exploration, and getting into places they shouldn’t be.
Flavor-wise, this works pretty well. There’s no combination of two of these classes that feels strange on its own and therefore all three don't, either. The character can be flamboyant or a complete under-the-radar enigma and it will make total sense either way.
As with any triple-class combo, you’ll want to select a primary class and two secondary ones. Making bard that primary class is the best for spellcasting, especially if combined with tertiary caster archetypes for ranger and rogue. Making that class ranger makes you the best at exploration and direct combat, and opting for rogue will likely mean an emphasis on stealth and damage.
[[Synergy Feats for Multiclassers#Bard w/ Ranger w/ Rogue|Bard - Ranger - Rogue chains and ideas]]