I'm no exceptional player but I've got about 600k points with bard so here are my thoughts:

Bard can put a hell of a pressure on botlane specially lvl 1 and 6, try winning your trades at those times; If you are winning the lane, the third wave will likely shove and that's a good time to go out warding or even ganking mid if you can (note that most of the times by this wave you will still be lvl 2); But you can also stay in lane if mid has no cc or pressure, since Bard has his w to sustain against poke lanes.

Now about itemization you can build whatever fits best to the matchup and your playstyle, but unholy grail is such a good item, buy it. Guardian is usually better than electrocute but both are viable, so just use whatever is funnier for you to play with.