Just a couple comments .. though hopefully the thread isn’t too old
1) consider a 2 level multiclass into hex blade warlock if it fits your character concept
- hex, shield, extra cantrip
- hexblades curse
- eldritch blast + agonizing blast
- 2 short rest first level spell slots
- additional invocation of choice
- medium armor proficiency, martial weapon proficiency
- charisma as attack stat for one weapon
This approach picks up a number of the useful spells that might be chosen using magical secrets but it also gives the bard competitive at will ranged damage when that is needed. I’ve run across a number of encounters where I pinned down opponents using hypnotic pattern and then either used blindness or eldritchblast (vicious mockery isn’t nearly as effective).
2) magical secrets
Counterspell - As mentioned, counterspell is a very popular option because bards are one of the best classes to use the spell and in a situation where you need it, it is critically important. Stopping confusion, hypnotic pattern, and other spells cast on your party is an essential skill. These spells when used by the party can completely change an encounter and the same goes when they are used against you.
Haste/slow - these can be good spells but both are concentration. Slow allows a save every turn, opponents still get an action, it is a wis save .. the only real advantage over hypnotic pattern is 40ft cube vs 30ft cube.
Haste .. gives one party member one extra attack. Again situational, but I would rather lock down opponents with hypnotic pattern or use hex+eldritch blast to typically do far more damage than one extra attack from a melee character.
Fireball/other AOE direct damage - non concentration, does substantial damage, fairly common resist, however, it adds to the bards ability to deal with larger numbers of weaker creatures.
Aura of Vitality - decent healing - concentration and uses bonus action. Very good between combat spell. Less useful in combat since a bard is probably better off using hypnotic pattern or another area control/debuff .. stopping three creatures from doing any damage is far more than 2d6/turn and there is always healing word to revive a downed party member. Healing Spirit is the same.
Fly - concentration but can be situationally useful especially out of combat .. but an instrument of the bards or winged boots could provide almost the same capability
Mirror image/misty step - both possibly decent to increase bard survivability
Find familiar - awesome scout plus they can execute the help action to assist a party member on attack. This works well with a party rogue but there are probably better mechanical choices .. decent for role playing too.
Level 10 magical secrets offers a huge range of choice.
Wall of force - concentration - up to 10 minutes - destroyed by disintegrate. This can be very effective crowd control covering a range of situations that can’t be addressed with hypnotic pattern.
Anyway, the key thing to keep an eye on is the competition of these spells for concentration, the save required (you don’t want everything to be a wisdom save), and the utility both in and out of combat. If you think a spell is too situational, it may not be a good choice for a bard who has a limited set of spells.