How/What BAs and Reactions to get on a Battle Master?

[BullHorn]

I just joined a level 8 campaign as a Fighter Battle Master and quickly realized that this subclass has absolutely no BAs or Reactions. He does have a once-per-short-rest Reaction heal and can expend his Superiority Dice to perform BAs and Reactions (if you choose them), but he has no 'free' BAs or reactions.

What's a smart way to acquire either or both? I plan to take Shield Master at level 10, if I survive long enough.

[nickl_2000]

Not full, but some decent choices as a Fighter.

Riposte Battle Master Maneuver - Reaction
Parry Battle Master Maneuver - Reaction
Rally Battle Master Maneuver - Bonus Action
Protection Fighting Style - Reaction
PAM - Reaction and Bonus Action
Shield Master - Reaction and Bonus Action
Mage Slayer - Reaction
2 Weapon Fighting - Bonus Action
Sentinel - Reaction
1 Level into Warlock/MI: Warlock for Hex - Bonus Action
2 levels in Ranger for Hunter's Mark - Bonus Action
Crossbow Mastery - Bonus Action
Defensive Duelist - Reaction

[Demonslayer666]

I second Sentinel as a good option. It was the first thing to come to mind. Riposte is also a good one.

Everyone has the BA of an off hand attack (2 weapon fighting as nickl_2000 mentioned).

[Willie the Duck]

Regardless, yes, both the battlemaster and champion fighter archetypes do not have much default BA or reaction effects. Guessing at developer intent is a fool's errand, but to be a fool for a moment, I think it is deliberate. It allows you to choose combat feats as appropriate to the character type you want, and not have said feats' BAs/reactions step on the toes of the archetype's.

PAM, Sentinel, and Shield Master (DM ruling dependent) are all great choices.

[Keravath]

If you are building the character from scratch then the best options are

Pole Arm Master for a melee fighter
Cross bow expert for a ranged fighter

Both of these give a bonus action attack every turn.

You can then also take GWM or Sentinel on a melee build and Sharpshooter on a ranged build.

If you start variant human you can have your primary attack stat of dex or wis at 20 and either PAM/GWM or Sentinel or Xbow Xpert/Sharpshooter at level 8.

Choose maneuvers to support the style you choose but if you take GWM/Sharpshooter then precision strike is very useful.

By the way, fighter doesn't get an ASI at level 10 so you won't be able to add one then. The next ASI is at 12.

P.S. If you have the stats you could go battlemaster 6 / warlock 2. You will still have an 18 attack stat with variant human plus a couple of level 1 spell slots, some spell and cantrip choices and a couple of invocations that can really support role play (Mask of Many Faces for instant disguises for example), Silent Image at will, Devils sight so you can see in the dark as a human and other options. The hex spell also can boost your damage but competes for bonus action use so it is a judgement call about when to use it.

A variant human using point buy can start with Xbow expert, 10-16-14-10-10-14 point buy stats, and end up at level 8 as either a pure battlemaster or battlemaster/warlock. The first is probably slightly more combat effective while the later has some spells and additional features that could be interesting depending on how you want to play the character (I'd probably go with devils sight+ one other invocation on a variant human since being able to see perfectly in the dark can be very useful).