Try to stay in lane untill atleast level 3, so you have will have of your important abilitys's. Make sure you pushed the wave up, otherwise a 1v2 for your adc becomes very hard and she will just lose cs and get tilted. On your first recall, buy ionian boots. Make sure to abuse his cvery strong level 1, because you will get good trades out of it.

In the mid game, you just want to roam, and look for ganking oppertunities, to stack your dark steal. If you use spellbook Bard, you can also try to steal objectives. Watch out that you dont overvalue your chimes, of you walk 30 seconds for 1 chime, you miss a lot of xp and you will fall behind. Try to wait a little longer until more chimes spawn.

Get as much wards done as possible, because vision is very important late game. Try to ult the enemy backline in team fights, so it becomas a 3v5, and if their support is ulted they dont get enough healing, winning you the fight. Help your team With objectives, and keep stacking chimes.

If you wanna have impact on objectives and steal them, spellbook Bard is for you. If you swap to smite, its instantly ready, unlike the other summoner spells. But remember, you cant swap in combat, so swap before going to the pit. I recommend going in with your flash, since its a little more reliable than your E. Use your E to escape, and if they folow you use your Q to stun them. Because you cant swap to the same spell with spellbook, your smite won't be up for the next dragon, so if you really want to steall all objectives, just play jungle.

The most important thing with bards ult, is practice it. Its hard to use and you just have to use it alot to get familiar with it. There are three major ways to ue your ult:
1. As cc. In this case you want to use your ult to slow stun the enemy, so you can get closer and prepare for a good Q.
2. As a team Zhonya's. Use your ult defensively when the enemy uses a ult that impacts your whole team, for example karthus or maokai.
3.Winning teamfights. especially in late game, bards ult can be game deciding. If you use your ult correctly and ult the enemy backline, you can make it a 3v5 in 1 second, winning you the teamfight. But if you use it on your own team, you can lose the game for your team.

Is Bard stillw orth picking up after the nerf? Yes definitly they only nerfed his early game damage, but once you picked up five chimes its back to the old. Your Q is still very strong early game, so you should still abuse that.