Odd scores are worthless to you, since you’re primarily interested in your modifier (which halves the number and drops the fraction), and just about all bonuses to ability scores come in even numbers. So you’ll get the most immediate bang for your buck by upping the odd scores to the next (even) number. So +1 Cha, +1 Con, +1 Str, +1 Wis, probably in that order, would take you to level 16. At level 20, the last one would probably go into Charisma; at those levels you can get an odd bonus to ability scores using wish or the associated tomes/manuals.
This has nothing to do with bard, aside from how we order them, it’s just a reaction to the very awkward situation where you have so many odd ability scores. You also have very good scores, which makes improving secondary and tertiary scores much less important than it usually is.
To address bard specifically, it helps to choose a focus. Making an attack-bard takes different equipment and feats than a caster bard. Even within the “attack-bard” sphere, melee and range are very different. Part of the bard’s strength is being a solid jack-of-all-trades, and he is that, but your feats and equipment tend to work better if you focus; the aspects that you focus less on, you’re relying on the solid bard chassis to keep you competent in. So if you focus on spellcasting, your feats and items are mainly geared towards those, but you’re a far better fighter than a wizard is1 just because of the things that bard automatically gives you.
Unfortunately, Pathfinder has pretty significantly nerfed the bard (disadvantageous changes to bardic music, loss of options available in 3.5 supplements), but my discussion of the 3.5 bard’s options may nonetheless be useful to you.
1 In theory, and in practice if the wizard ignores mundane fighting. In reality, with a little effort, the wizard can be better at it than a bard. The wizard can be better than almost anyone at almost anything with a little effort, unfortunately.